JPS607615A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a high density recording medium having excellent oxidative stability, shelf life and still durability by incorporating metallic magnetic powder of which the differential thermal analysis curve does not change up to a specific temp. into a magnetic layer with high dispersibility by using an anionic or nonionic dispersant. CONSTITUTION:A magnetic layer contg. metallic magnetic powder of which the differential thermal analysis curve does not change up to at least 80 deg.C, i.e., metallic magnetic powder having good oxidative stability and an anionic or nionic dispersant at 1-20pts.wt. to 100pts.wt. a binder is coated on a base. The above- mentioned metallic magnetic powder having good thermal stability is obtd. by coating the outside surface of metallic magnetic powder 1 with a thermally stable high polymer compd. 2 such as polyamide resin or the like or oxidizing gradually the outside surface of the metallic magnetic powder to form a stable oxide layer. The magnetic recording medium having uniform dispersion of the magnetic powder and an excellent shelf life is thus obtd.

Description

Detailed Description of the Invention (a) Industrial Application Field: The present invention relates to a magnetic recording medium, and more specifically, provides a magnetic recording medium with excellent oxidation stability, storage stability, and still durability. This is what I am trying to do.

(b) Prior art: Magnetic recording media such as audio tapes and recording tapes are produced by coating magnetic powder on a support such as polyethylene terephthalate using a material such as vinyl chloride-vinyl acetate copolymer, cellulose resin, epoxy resin, polyurethane resin, etc. A magnetic layer is formed by coating and drying a magnetic paint obtained by mixing and dispersing a binder.

Metal magnetic powder is superior to oxide-based magnetic powder in terms of angularization (residual magnetization/saturation magnetization ratio), high saturation magnetization, and high coercive force as a magnetic powder contained in magnetic paint. , widely used. However, metal magnetic powder is so active against oxygen that it ignites at room temperature (15 to 40°C), the powder surface is easily oxidized and corroded, and magnetic recording media using metal magnetic powder have poor storage stability. Ta.

■ Compared to the conventionally widely used oxide-based magnetic powders such as iron oxide and chromium oxide, it has a much larger magnetic moment and therefore tends to generate larger interaction forces between particles.
Particles agglomerated and could not be well dispersed in the binder.

■ Due to high-density recording, dispersibility becomes even worse when the particles are less than 1 μm. In addition, the surface area increases, making it more likely to be used for important jobs, rusting easily, and decreasing storage stability and still durability.

■ In particular, in the case of video tapes, when playing back still images, the tape is brought into strong sliding contact with the magnetic head and is repeatedly run over the same spot several dozen times for 7 seconds, so the metal magnetic powder contained in the magnetic layer does not fall off. , causing clogging of the magnetic head.

(2) Moreover, by repeatedly scanning the tape, the tape temperature rises to 50 to 70°C, further promoting the oxidation of the metal magnetic powder.

The reason why the metal magnetic powder lacks oxidation stability may be due to the inherent properties of the metal magnetic powder, but it is said that the cause is pinholes on the surface of the metal magnetic powder.

Through differential thermal analysis of metal magnetic powder and observation of the powder surface using an electron microscope, the present inventors found that the temperature at which the differential thermal curve of known metal magnetic powder that has been widely used is 20 to 75°C. In the range of The surface is relatively smooth, suggesting the presence of many pinholes. On the other hand, the surface of metal magnetic powder whose differential thermal curve does not change up to at least 80°C is quite rough, as shown in Figure 2 (30,000 times magnified photograph), which is similar to the powder surface in Figure 1. A comparison suggests that there are fewer pinholes.

Therefore, it is assumed that if a magnetic recording medium is manufactured using a metal magnetic powder whose differential thermal curve does not change up to at least 80°C, a magnetic recording medium with high oxidation stability (storage stability) can be manufactured. The present invention was carried out. However, even if you simply create a magnetic paint using a conventional blending method and ingredients using a metal magnetic powder whose differential thermal curve does not change up to at least 80°C, a satisfactory product in terms of dispersibility cannot be obtained. In other words, a metal magnetic powder whose differential thermal curve does not change up to at least 80° C. has a high saturation magnetization, and the interaction force between the magnetic powder particles is large, so particles tend to aggregate and cannot be dispersed.

Of course, in the case of commonly used metal magnetic powders, a method has been used in which a cationic dispersant is blended as a component of a magnetic powder-containing composition, but this method is not always satisfactory.

In view of these circumstances, the inventors of the present invention have conducted various experiments to improve the dispersibility of metal magnetic powder whose differential thermal curve does not change up to at least 80°C, and have decided to use an anionic or nonionic dispersant. The inventors have discovered that the dispersibility of the metal magnetic powder can be improved by doing so, and have arrived at the present invention.

(c) Object of the invention: That is, an object of the invention is to provide a magnetic recording medium containing highly dispersible metal magnetic powder whose differential thermal curve does not change up to at least 80°C.

Another object of the present invention is to provide a magnetic recording medium with excellent oxidation stability, storage stability, and methyl durability.

(d) Structure of the invention: The object of the present invention is to provide on a support a magnetic layer containing a metal magnetic powder whose differential thermal curve does not change up to at least 80°C and an anionic or nonionic dispersant. achieved by.

The metal magnetic powder used in the magnetic layer of the magnetic recording medium of the present invention includes Fe-Ni-Co alloy, Fe-Mn-Zn
Alloy, Fe-Co-Ni-P alloy, Fe-N1-ZH
Gold alloy Fe-Ni-0r-P alloy, Fe-Co-N
i-Cr alloy, Fe-C.

P alloy, Fe-Ni alloy, Fe-Ni-Mn alloy, Co
-Ni alloy, Co-N1-P alloy, Fe-At alloy, F
e-Mn-Zn alloy, Fe-At-P alloy, etc. Fe S
Examples include metal magnetic powder containing N 1% Co as a main component.

A stable metal magnetic powder whose differential thermal curve does not change up to at least 80°C (hereinafter simply referred to as "magnetic powder" for convenience).

) can be obtained using the following method.

(1) As shown in Figure 3, the outer surface of the metal magnetic powder is coated with a thermally stable polymer compound (e.g. polyamide resin).
Method of covering with 2.

(2) As shown in FIG. 4, a method of slowly oxidizing the outer surface of the metal magnetic powder material to form a stable oxide layer 3.

(3) Add various additives to the alloy components of the metal magnetic powder, such as nickel, aluminum, silicon, magnesium,
This is a method in which steel, various elements such as phosphorus, and/or compounds thereof are added by inclusion or deposition.

The metal magnetic powder contained in the magnetic layer of the magnetic recording medium of the present invention may be prepared by any of the above methods, but mainly (
It is preferable that the magnetic powder obtained by the method 3) is used as the basis, and it is preferable that one or both of the methods (1) and (2) be used as an auxiliary method, if necessary. In other words, in the magnetic powder obtained by method (1), the proportion of metal magnetic powder (magnetic material) itself per unit volume of magnetic powder is small, and the amount of magnetization per unit volume of the magnetic layer is , is smaller than that when uncoated metal magnetic powder is used. For example, in a coated magnetic recording medium in which the magnetic layer is mainly formed of magnetic powder and a binder, the metal magnetic powder to be contained in the magnetic layer is
When thermal stability (or oxidative stability) is achieved by the method described in (1) above, the actual filling rate of the magnetic material in the magnetic layer becomes low, which makes it difficult for recording media to perform high-density recording. undesirable in some cases. In addition, the magnetic powder obtained by method (1) requires special measures for the binder system (use of a special binder, special dispersant, etc.), and has the disadvantage of complicating production.

The magnetic powder obtained by method (2) also has the same drawbacks as the magnetic powder obtained by method (1).

In other words, the volume of the part that is not slowly oxidized, in other words, the volume of the non-oxidized part that contributes to magnetization, is smaller than the volume of the magnetic powder, as in the case of (1), so the filling of the magnetic material in the magnetic layer is rate decreases.

Therefore, the magnetic powder used in the magnetic layer of the magnetic recording medium of the present invention is a magnetic powder other than one coated with a slow oxidation film, and the powder itself has thermal stability (or oxidation stability). is preferable, and if necessary (
1) or (2), or a combination of these methods is preferable.O In addition, methods (1), (2), or other methods, such as magnetic powder, can be applied to a pinhole in the magnetic powder. A thin film is formed on the surface of the magnetic powder by immersion in a solution of a substance (which may be a low-molecular compound or a high-molecular compound) that has the property of filling the magnetic powder, or by immersion or the method described in (1) above. Formability and thermal stability may not be sufficient. ), this can be chemically or physically reacted to form a thermally or oxidatively stable magnetic powder. Further, antirust treatment using silicone oil or the like can also be combined. In short, the magnetic powder of the present invention has been modified to be thermally or oxidized stable up to at least 80°C to the extent that the metal magnetic powder does not significantly impair its magnetic properties. It is a metal magnetic powder with no change in differential thermal curve.

Among the above-mentioned methods (1) to (3) and other methods, method (3), which is mainly used, will be described in detail.

Metal components of metal magnetic powder (here, metal components mainly include carbon, which is not detected by an X-ray microanalyzer,
It means components other than hydrogen, oxygen, etc. In the method (3) of adding various elements and/or compounds to (3), preferred additives include aluminum, silicon, nickel, and compounds thereof.

A differential thermal curve is a method that measures the temperature difference that occurs between Mesil magnetic powder and a reference material such as thermally stable alumina or quartz at a constant rate, and determines the energy state of both. The measurement method is, for example,
It is described in detail in "New Experimental Chemistry Course 2, Basic Technology" edited by the Chemical Society of Japan.

When the additive is AL and/or its compound, the amount of addition is such that the proportion of A71° atoms (for example, At2 if the additive is AL203) in the metal components of the metal magnetic powder is equal to the total metal content. 0.5 to 2 based on the atomic weight of the component
The range is 0 atomic weight, and particularly preferred is 1 to 2.
It is in the range of 0 atomic weight. If the At atom content is less than 0.5 atomic weight %, the thermal or oxidative stability of the obtained metal magnetic powder will be insufficient, and the characteristics of the magnetic recording medium prepared using this magnetic powder, such as storage stability, The playback quality and still durability become insufficient.

In addition, when the St element and/or its compound is used as an additive, the metal component part (At, si %Ss Fes N
is C05RaXHl cu, p, Zns seed, Cr,
The weight percentage occupied by Sl atoms is 1% or less, preferably 0.5% by weight or less, and may be 0.1% or less in some cases. When St is outside this range, it may be difficult to modify the magnetic powder.

Furthermore, when containing Ni element and/or a compound thereof as an additive, it is desirable that the upper limit is 30 atomic weight % or less, preferably 20 atomic weight % or less from the viewpoint of magnetic properties.

Conventionally, anionic, nonionic, cationic, and amphoteric dispersants have been known as dispersants that can be used in the magnetic layer of magnetic recording media.
It has been found that anionic and nonionic dispersants are suitable as dispersants for metal magnetic powders that do not change up to ℃.

On the other hand, it has become clear that still durability does not improve with cationic materials.

The reason why cationic dispersants are disadvantageous for metal magnetic powders whose differential thermal curves do not change up to at least 80°C is that cationic dispersants are less convenient for metal magnetic powders than anionic and nonionic dispersants. This may be because the area required for adsorption (occupied area) is small (however, the occupied area here is not particularly related to the ease of adsorption of the dispersant to the magnetic powder).

Therefore, in order to achieve sufficient dispersion due to the small occupied area, it is necessary to increase the ratio of the cationic dispersant to the metal magnetic powder, and if this is increased, the dispersant may bleed out. On the other hand, regarding ease of adsorption, which is unrelated to occupied area, it is thought that cationic dispersants tend to be difficult to adsorb to the metal magnetic powder.

When the metal magnetic powder whose differential thermal curve does not change up to at least 80°C is surface-treated and the treated metal magnetic powder is dispersed and contained in the magnetic layer, the differential thermal curve is at least 80°C.
Anionic or nonionic surfactants are used for surface treatment of metal magnetic powders that do not change up to 0°C, but when dispersing the treated metal magnetic powders in the magnetic layer, the dispersants to be included may be anionic, nonionic, or amphoteric. (e.g. lecithin) is good.

Examples of the anionic dispersant include (1) carboxylic acid salts, (2) sulfuric acid ester salts, (2) sulfuric acid ester salts, (2) dithiophosphoric acid ester salts, and (2) sulfonic acid salts. However, salt means salts of ammonium, alkali metals, alkaline earth metals, etc.

In addition, fatty acids can also be used as anionic dispersants.

As carboxylic acid salt dispersants, there are salts of saturated and unsaturated fatty acids having 6 to 32 carbon atoms, and unsaturated fatty acid salts are particularly preferred.

The sulfate ester salt type dispersant has 6 to 1 carbon atoms.
Sulfuric ester salt of 8 higher alcohols, 6 carbon atoms
~32 fatty acid higher alcohol sulfate ester salts,
Sulfate ester salt of higher alcohol of fatty acid ester having an alkyl group having about 1 to 4 carbon atoms as a substituent, sulfate ester salt of higher alcohol of polyoxyethylene alkyl ether: R(C2H40)110SO;M" (However, 1 (n(,6, M is an alkali metal atom) R is an alkyl group having 8 to 18 carbon atoms 0 As a phosphate ester salt-based dispersant, phosphorus of a higher alcohol having 6 to 18 carbon atoms is used. Acid monoester salts, phosphoric acid diester salts, and dithiophosphoric acid ester salts such as cynic acid ester salts of compounds obtained by adding ethylene oxide to higher alcohols having 6 to 18 carbon atoms (in this case, zinc salts are included).
etc.

More specifically, for example, sodium caproate, potassium erucate, sodium caprylate, magnesium caprylate, sodium pelargonate, ammonium pelargonate, sodium caprate, magnesium caprate, sodium undecylate, magnesium undecylate, undecylic acid. Sodium, sodium undecylate, sodium diurate, ammonium laurate, magnesium laurate, potassium lauroleate, magnesium diuroleate, sodium tridecanoate, calcium tridecanoate, sodium myristate, potassium myristate, ammonium myristate, magnesium myristate , sodium tudate, ammonium tudate, magnesium tudate, sodium pentadecanoate, sodium valmitate, ammonium palmitate, magnesium palmitate, sodium seamarate, ammonium seamarate, magnesium seamarate, sodium margarate, margaric acid Ammonium, calcium margarate, sodium stearate, potassium stearate, ammonium stearate, magnesium stearate, calcium stearate, sodium petroselate, magnesium petroselate, lithium oleate, sodium oleate, potassium oleate 1, ammonium oleate, olein Magnesium elaidate, calcium oleate, barium oleate, sodium elaidate, potassium elaidate, ammonium elaidate, magnesium elaidate, calcium elaidate, sodium ricinoleate, potassium ricinoleate, magnesium ricinoleate, sodium linoleate, eleostearin Potassium acid, sodium linoleate, potassium lyrunate, sodium valinarate, potassium valinarate, sodium nonadecanoate, ammonium nonadecanoate, magnesium nonadecanoate, sodium arachinate, ammonium arachinate, magnesium arachidate, sodium arachidonate, potassium arachidonate , sodium caprate, ammonium caddate, magnesium caprate, sodium heneicosanoate, sodium behenate,
Behe: y acidity v tm, ammonium behenate, calcium behenate, magnesium behenate, sodium erucate, potassium erucate, magnesium erucate, calcium erucate, ammonium erucate, sodium pussidate, ammonium brassidate, Magnesium brassidate, sodium lignocerate, potassium lignocerate, ammonium lignocerate, calcium lignocerate, magnesium lignoserate, sodium cerotate, potassium cerotate, ammonium cerotate, magnesium cerotate, sodium montanate, potassium montanate, montanic acid calcium,
Fatty acid salts having 6 to 32 carbon atoms such as magnesium montanate, calcium montanate, sodium melisinate, potassium melisinate, ammonium melisinate, magnesium melisinate, sodium heptanooleyl phosphate, sodium dogucyl phosphate, etc. Examples include phosphoric acid ester salts.

Among these anionic dispersants, those preferred for use in the present invention are fatty acid salts having 11 to 18 carbon atoms. In particular, unsaturated fatty acid salts (eg, oleate) are more effective than saturated fatty acid salts (eg, stearate), and are therefore preferred.

Nonionic dispersants include: ■ Sorbitan fatty acid ester, O propylene gelcol fatty acid ester, θ polyethylene glycol fatty acid ester, [phase] polyoxyethylene alkyl ether, R-0-(C2H40)nH
.

However, 2 (n (5 ■) Polyoxyethylene alkyl phenyl ether etc. are mentioned. As the sorbitan fatty acid ester,
Specific examples include sorbitan monopalmitate, sorbitan monostearate, sorbitan sesquistearate, and sorbitan trispearate. In addition, examples of propylene glycol fatty acid esters include monostearate and the like.

The magnetic layer of the magnetic recording medium according to the present invention has the differential thermal curve of at least 80'C'! ! A magnetic paint obtained by kneading metal magnetic powder that does not change with water, a binder that binds the metal magnetic powder, and the above-mentioned dispersant and other additives such as an abrasive and an antistatic agent is coated on a support. Formed by drying.

Examples of binders that can be used in the magnetic layer of the magnetic recording medium of the present invention include thermoplastic resins, thermosetting resins, reactive resins, electron beam curable resins, and mixtures thereof.

The thermoplastic resin has a softening temperature of 150°C or less and an average molecular weight of 10,000 to 200,000. The degree of polymerization is 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, methacrylic acid ester-vinylitine chloride copolymer, methacrylic acid ester-
Ethylene, tt4i combination, urethane elastomer, polyvinyl fluoride, vinylidene chloride-acrylonitrile copolymer, acrylonitrile-butadiene copolymer, polyamide resin, polyvinyl butyral, cellulose derivative (cellulose acetate butyrate), cellulose diacetate, cellulose triacetate, cellulonispropionate, nitrocellulose, etc.), styrene-butadiene copolymers, polyester resins, chlorovinyether-acrylic acid ester copolymers, amine resins, various synthetic rubber-based thermoplastic resins, and mixtures thereof, etc. is used.

These resins are disclosed in Japanese Patent Publications Nos. 37-6877 and 39-1.
No. 2528, No. 39-19282, No. 40-5349
No. 40-20907, No. 41-9463, No. 4
No. 1-14059, No. 41-16985, No. 42-6
No. 428, No. 42-11621, No. 43-4623, No. 43-15206, No. 44-2889, No. 44
-17947, 44-18232, 45-14
No. 020, No. 45-14500, No. 47-18573
No. 47-22063, No. 47-22064, No. 47-22068, No. 47-22069, No. 47-
No. 22070, US Pat. No. 48-27886, US Pat. No. 3,144,352, US Pat. No. 3,419,420
No. 3,499,789, No. 3,713
, No. 887, No. 8A.

1 as a thermosetting resin or reactive resin in the form of a coating solution.
It may have a molecular weight of 0,000 to 200,000, and may have an infinite molecular weight due to reactions such as condensation and addition after coating and drying.

Moreover, among these resins, those that do not soften or melt before the resin is thermally decomposed are preferable.

Specifically, for example, phenolic resin, epoxy resin,
Polyurethane curable resins, urea resins, melamine resins, alkyd resins, silicone resins, acrylic reactive resins, mixtures of high molecular weight polyester resins and incyanate prepolymers, mixtures of methacrylate copolymers and diisocyanate prepolymers, polyester polyols and These include mixtures of polyisocyanates, urea formaldehyde resins, mixtures of low molecular weight glycols/high molecular weight diols/triphenylmethane triisocyanates, polyamine resins, and mixtures thereof.

These resins are disclosed in Japanese Patent Publication Nos. 39-8103 and 40-9.
No. 779, No. 41-7192, No. 41-8016,
No. 41-14275, No. 42-18179, No. 43
-12081, 44-28023, 45-14
No. 501, No. 45-24902, No. 46-13103
No. 47-22067, No. 47-22072, No. 47-22073, No. 47-28045, No. 47-
No. 28048, US Pat. No. 47-28922, US Pat. No. 3,144,353, US Pat. No. 3,320,090
No. 3,437,510, No. 3,597,27
No. 3, No. 3,781,210, No. 3,781,2
It is described in the specification of No. 11.

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 acrylic type, etc. Examples include phosphoric acid ester acrylic type, aryl type, and hydrocarbon type.

The above binders may be used alone or in combination, and other additives may be added if necessary.

The mixing ratio of magnetic powder and binder is 100% magnetic powder.
The binder is mixed in an amount of 5 to 400 parts by weight, preferably 10 to 200 parts by weight. If the amount of binder mixed is too large, the recording density of the magnetic recording medium will be reduced, and if it is too small, undesirable situations such as weak strength of the magnetic layer, decreased durability, and powder falling will occur.

Additionally, various hardening agents can be added to the magnetic layer to improve the durability of the magnetic recording medium. for example,
It can contain polyfunctional incyanate and the like.

Examples of polyfunctional isocyanates include tolylene diisocyanate), 4,4'-diphenylmethane diisocyanate, naphthylene diisocyanate, hexamethylene diisocyanate, cyclohexane diisocyanate, adducts of diisocyanates and trivalent polyols, or 5 amounts of diisocyanates. Examples include the body.

Furthermore, an adduct of 1.3 mol of tolylene diisocyanate and 1 mol of trimethylolpropane, an adduct of 3 mol of metaxylylene diisocyanate and 1 mol of trimethylolpropane, a pentamer of tolylene diisocyanate, and 2 tolylene diisocyanate A pentamer consisting of moles, etc. can be used.

In addition to the metal magnetic powder, binder, dispersant, and hardening agent described above, the magnetic layer contains other dispersants, abrasives,
Antistatic agents, etc. may be added. ○ Dispersants used include carbon atoms such as caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, elaidic acid, linoleic acid, lylunic acid, etc. Number 8 to 18 fatty acids (represented by R-COOH, R is 7 carbon atoms)
~17 saturated or unsaturated alkyl groups): metal soaps consisting of alkali metals (Li% Na5K, etc.) or alkaline earth metals (Mg, CaX'Ba, etc.) of the above-mentioned fatty acids: lecithin, etc. are used. . In addition to this, higher alcohols having 12 or more carbon atoms, and in addition to these,
Sulfuric esters and the like can also be used.

These dispersants may be used alone or in combination of two or more. These dispersants are added in an amount of 1 to 20 parts by weight based on 100 parts by weight of the binder.

These dispersants are described in Japanese Patent Publication Nos. 39-28369, 44-17945, 48-15001, U.S. Patent Nos. 3,587,993, 3,47
It is described in the specification of No. 0,021, etc.

As a lubricant, silicone oil, carbon black,
Graphite, carbon black graft polymer, molybdenum disulfide, tungsten disulfide, 12 carbon atoms
It can also be used for fatty acid esters (so-called waxes) consisting of ~16 monobasic fatty acids and monohydric alcohols having a total number of carbon atoms of 21 to 23 carbon atoms. These lubricants are added in an amount of 0.2 to 20 parts by weight based on 100 parts by weight of the binder. Regarding these, please refer to Special Publication No. 43-23889 and No. 43-81543.
Publication specification, U.S. Patent No. 3,470,021, U.S. Patent No. 3,492,235, U.S. Patent No. 3,497,411, U.S. Patent No. 3,523,086, U.S. Patent No. 3,625,720 ,
Same No. 3,630,772, Same No. 3,634,253, Same No. 3.630,772, Same No. 3,634,253
No. 3,642,539, No. 3,687,72
IBM Technical Disclosure Plutan Magazine Volume 9, No. 7, Page 779 (December 1966) (IBM Technical
Disclosure BulletinMol, 9
．． N[L9. Page779 (1966, Dec.
ember): Electronics Magazine No. 12, No. 3
80 pages (1961) (ELEKTRONIK, 12
．． Page 380.1961) etc.

Fused alumina, a material commonly used as an abrasive
Silicon carbide, chromium oxide, corundum, artificial corundum, artificial diamond, garnet, emery (main ingredients: corundum and magnetite), etc. are used. These abrasives have an average particle size of 0.05 to 5μ, and
Preferably it is 0.1-2μ. These abrasives are added in an amount of 0.5 to 20 parts by weight based on 100 parts by weight of the binder. These abrasive materials are described in Japanese Patent Application Laid-Open No. 1983
-115510 publication specification, U.S. Patent No. 3,007,
No. 807, No. 3,041,196, No. 3,687
, 725, British Patent No. 1,145,349,
It is described in West German Patent (DT-PS) No. 853,211.

If necessary, antistatic agents include conductive powders such as graphite, carbon black, tin oxide-antimony oxide compounds, tin oxide-titanium oxide-antimony oxide compounds, carbon black graft polymers, and natural surfactants such as saponin. Agent: Nonionic surfactant such as alkylene oxide type, glycerin type, glycidol type:
Cationic surfactants such as higher alkylamines, quaternary pyridines, other heterocycles, phosphoniums or sulfoniums: Anions containing one acidic group such as carboxylic acid, sulfonic acid, phosphoric acid, sulfuric ester group, phosphoric ester group, etc. Surfactants Ampholytic surfactants such as diamino acids, nosulfonic acids, sulfuric acid and 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. Patent No. 2,271,623, U.S. Pat.
No. 2.676,975, No. 2.691.5'
No. 66, No. 2,727,860, No. 2.730,
No. 498, No. 2,742,379, No. 2,739
, No. 891, No. 3,068,101, No. 3,15
No. 8,484, No. 3.201,253, No. 3.2
No. 10,191, No. 3.294,540, No. 3,
No. 415,649, No. 3,441,413, No. 3
．． No. 442,654, No. 3,475,174, No. 3,545,974, West German Patent Publication (OLS)
No. 1,942,655, British Patent No. 1,077,31
No. 7, No.
(Maki Shoten 1964 edition): "Surface Active Agents" by A. W. Peiri (Interscience
(1958 edition)
: "Encyclopedia of Surface Active Agents Volume 2" by T. P. Sisley (Kecal Publishing Company, 1964 edition): "Surfactant Handbook" 6th edition (Sangyo Tosho Co., Ltd., December 20, 1964) These surfactants, which are described in books such as Japan), may be added alone or in combination. Although these are used as antistatic agents, they are sometimes applied for other purposes, such as dispersion, improving magnetic properties, improving lubricity, and as coating aids.

The production of the magnetic recording medium according to the present invention includes the magnetic powder,
It is manufactured by cross-dispersing magnetic paint components such as a binder in a solvent to prepare a magnetic paint, and then applying the resulting magnetic paint onto a support and drying it.

In addition to the above-mentioned magnetic paint components, the magnetic paint may contain additives such as a dispersant, a lubricant, an abrasive, an antistatic agent, and the like, if necessary.

Solvents for magnetic paint or solvents used when applying magnetic paint include acetone, methyl ethyl ketone (MEK),
Ketones such as methyl in butyl ketone (MIBK) and cyclohexanone; alcohols such as methanol, ethanol, propatool, and butanol; methyl acetate, ethyl acetate, butyl acetate, 'A acid-1-fl, furovir acetate,
Ester systems such as ethylene glycol monoacetate, diethylene glycol dimethyl ether, 2-ethoxyethanol, tetrahydrofuran, dioxane, etc.: Aromatic hydrocarbons such as benzene, toluene, xylene, etc.: methylene chloride, ethylene chloride, carbon tetrachloride, chloroform, Halogenated hydrocarbons such as dichlorobenzene can be used.However, when mixing the magnetic paint components, the magnetic powder and other magnetic paint components are fed into the mixer all at the same time or individually one after another. For example, first, the magnetic powder is added to a solution containing a dispersant and kneaded for a predetermined time, and then the remaining components are added and mixed continuously to obtain a magnetic paint.

Various types of crosstalk devices are used to disperse crosstalk. For example, two roll mill, three roll mill, ball mill, pebble mill, sand grinder, Sjegvari
These include attritor, high-speed impeller dispersion machine, high-speed stone mill, high-speed impact mill, Disper Kneader-1 high-speed mixer, homogenizer, and ultrasonic dispersion machine.

When the magnetic paint according to the present invention is cross-dispersed by these methods, the dispersion is extremely good, and the number of aggregates when observed with an electron microscope is extremely small compared to the case of conventional magnetic paints. Ta.

Technologies related to crosstalk and dispersion are described in Chi O Paratong's ``
Paint Flow and Pigment Dispersion (1964, published by John Wiley and Nun)
J.T., 0. PATTON (Pa1nt Flow
and Pigment Dispersion (
1964, John Wllley and Son)
). Also, U.S. Patent No. 2,581,
No. 414 and No. 2,855,156.

However, regarding the manufacturing method of magnetic paint, Japanese Patent Publications No. 35-15, No. 39-26794, No. 43-186, No. 47-
No. 28043, No. 47-28045, No. 47-280
No. 46, No. 47-28047, No. 47-31445, No. 48-11162, No. 48-21332, No. 4
8-33683 and the specifications of each publication.

Materials for the support include polyesters such as polyethylene terephthalate and polyethylene-2,6-naphthalate, polyolefins such as polypropylene, cellulose derivatives such as cellulose triacetate and cellulose diacetate, plastics such as polycarbonate, and CuXAt.

Metals such as Zn, glass, so-called knee ceramics (
For example, various ceramics such as boron nitride, silicon carbide, etc. are used.

Support forms include tape, sheet, card, disk,
Any material such as a drum may be used, and various materials are selected as necessary depending on the form.

The thickness of these supports is approximately 3 mm in the case of tape or sheet form.
~100μ, preferably 5~50μ, and in the case of a paper, disk, or card, the diameter is approximately 30μ to 10μ, and in the case of a drum, the shape is cylindrical, and the shape is determined depending on the recorder used.

The surface of the support opposite to the side on which the magnetic layer is provided for the purpose of preventing static electricity, preventing transfer, etc. is a so-called Bacco
k Coat ).

Regarding backcoats, for example, U.S. Patent No. 2.80
No. 4,401, No. 3,293.066, No. 3,6
No. 17,378, No. 3,062,676, No. 3,
No. 734,772, No. 3.476,596, No. 2
, No. 643,084, No. 2,803,556, No. 2,887,462, No. 2,923,642, No. 2.997,451, No. 3,007,892 ,
Same No. 3,041,196, Same No. 3,115, 4.20
No. 3,166,688, etc.

In addition, in order to form a magnetic layer by coating the magnetic paint on the support, gravure roll coach ink, Meyer bar coating, Doc P-7'lade coating, reverse roll coating, dip coating, air knife coating, calendar coating, etc. Methods such as coating, skies coach ink, kiss coating, fan tin coating, etc. can be used, and other methods are also possible, and detailed explanations of these can be found in "Coating Engineering" (March 1970, Breakfast Shoten) Published, p. 258 et seq.) and [Plastic Films - Processing and Its Applications]
(published by Gihodo in 1971) is described in detail.

The magnetic layer coated on the support by such a method is
After performing a treatment to orient the magnetic powder according to the present invention in the layer, if necessary, the coated magnetic layer is dried. Also,
A magnetic recording medium is manufactured by performing surface smoothing processing and cutting into a desired shape if necessary.

The orientation method of the metal magnetic powder, which is contained in the magnetic layer of the magnetic recording medium according to the present invention and whose differential thermal curve does not change up to at least 80° C., is determined depending on its use.

[e) Effect: ■ The magnetic recording medium according to the present invention uses a metal magnetic powder whose differential thermal curve does not change up to at least 80° C. together with an anionic or nonionic dispersant in the magnetic layer. Even when the magnetic recording medium is repeatedly run, the magnetic powder is not easily oxidized, and the magnetic properties of the magnetic recording medium change little over time. In addition, (1) the differential thermal curve of the magnetic powder is stable up to at least 80°C; therefore, the degree of heat generated by friction between the magnetic head and the magnetic recording medium (equilibrium temperature 60°C) during recording or reproduction of the magnetic recording medium is (°C to 75°C), the magnetic powder does not change and the still durability of the magnetic recording medium is also excellent.

■ Since the magnetic powder whose differential thermal curve does not change up to at least 80°C is contained with enhanced dispersibility using an atheonic or nonionic dispersant, the resulting magnetic recording medium has high thermal stability of the magnetic powder itself, Due to the synergistic action with the above-mentioned dispersant, products with excellent wear resistance can be obtained.

(f) Examples: Next, the content of the present invention will be specifically explained based on Examples and Comparative Examples. In the examples and comparative examples, 1
The description ``parts'' shall mean ``parts by weight.''

Examples 1 to 7 The differential thermal curve listed in the second column of Table-1 is at least 80°C
Using metal magnetic powders (1) to (7) that do not change up to 0, metal magnetic powder-containing compositions were prepared according to the set-paraboloids and proportions shown in Table 2. (Nn4 CH2-cu2N[(%C)I, CH2-
M(Co-R-CON NH-+CH2-CH, NFI
-); G12CH, -Nu, where R is the trade name.

Margin table below - 2 After thoroughly mixing and dispersing each of the metal magnetic powder-containing compositions obtained using a ball mill, 5 parts of Coronet) L (product name: 2 polyisocyanate solution manufactured by Nippon Polyurethane Co., Ltd.) was added and mixed uniformly. Seven types of magnetic paints were obtained. For each of these magnetic paints, the contained metal magnetic powder (1), (2)
, (3), (4), (5), (6) and (7) magnetic paints (1), (2), (3), (4), (5), (
6) and (7).

Next, these magnetic paints (1) to (7) were applied, respectively.
The coating was applied to one side of seven types of separately prepared polyethylene terephthalate films each having a film thickness of 12 μm while applying a magnetic field of 2,000 Gauss to give a dry film thickness of 5 μm.

The resulting wide sample was subjected to supercalender treatment, and then cut to a width of 12.65 mm to produce a videotape. These video tapes were named Example Tape 7 based on the magnetic paints (1) to (7) applied to them, respectively.

Examples 8-14 Seven videos were prepared according to the same treatments and steps as Examples 1-7, except that potassium alkylbenzenesulfonate (anionic dispersant) was used instead of sodium stearate (anionic dispersant). A tape was made. These video tapes were named Example tapes 8 to 14, respectively, depending on the methane magnetic powders (1) to (7) contained in the applied magnetic paint.

Examples 15-21 The same treatments and steps as Examples 1-7 were followed except that sulfosuccinic acid di-2-ethylhexyl ester sodium salt (anionic dispersant) was used instead of sodium stearate (anionic dispersant). Seven types of videotapes were made. Metal magnetic powder (1) to (7) contained in the magnetic paint applied to these videotapes
Accordingly, they were named Example Tapes 15-21, respectively.

Examples 22 to 28 Polyoxyethylene alkyl ether ((C2H40
Seven types of videotapes were produced using the same five treatments and steps as in Examples 1 to 7, except that a nonionic dispersant (nonionic dispersant) was used (n = 16) (nonionic dispersant). These video tapes were named Example tapes 21''-28, respectively, according to the metal magnetic powders (1) to (7) contained in the applied magnetic paint.

Examples 29 to 35 Polyoxyethylene alkyl ether ((C2H40
Seven types of videotapes were produced using the same treatments and steps as in Examples 1 to 7, except that a nonionic dispersant was used (n = 18) (nonionic dispersant). For these video tapes, Example tapes 29 to 35 were prepared according to the metal magnetic powders (1) to (7) contained in the applied magnetic paint.
It was named.

Comparative Example 1 A silicone oil film was formed on the surface of the metal magnetic powder whose differential thermal curve tends to change easily at room temperature, and the temperature at which the differential thermal curve started changing was 50°C.
A videotape was produced using the same treatment and steps as in Example 22, except that the magnetic powder was used. This videotape was named Comparative Example Tape 2.

Comparative Example 3 A silicone oil film was formed on the surface of the metal magnetic powder whose differential thermal curve tends to change easily at room temperature, and the temperature at which the differential thermal curve started to change was set at 50°C.
A videotape was produced using the same treatment and steps as in Example 29, except that the magnetic powder obtained in Example 29 was used. This videotape was designated as Comparative Example Tape 3.

Comparative Example 4 In place of the metal magnetic powder (1) in Table 1, a silicone oil film was formed on the surface of the metal magnetic powder whose differential thermal curve started changing temperature was room temperature, and the differential thermal curve started changing temperature was 5
Except that the temperature was 0°C and octadecyl ammonium chloride (cationic dispersant) was used instead of sodium stearate (anionic dispersant).
A videotape was produced using the same treatment and steps as in Example 1.

The obtained videotape was named Comparative Example Tape 4 and was subjected to the same treatment and steps as in Example 1, except that metal magnetic powder whose temperature at which the differential thermal curve started changing was set at 73° C. by oxidation was used. A videotape was made.

The resulting videotape was named Comparative Example Tape 5.

Comparison Example 6 Same as Example 22, except that instead of the metal magnetic powder (1) of Mourning-1, a metal magnetic powder whose surface was slowly oxidized and the temperature at which the differential thermal curve started changing was 73°C was used. Videotapes were made using similar processes and steps.

The obtained videotape was designated as Comparative Example Tape 6.

Comparative Example 7 Same as Example 37 except that instead of metal magnetic powder (1) in Table 1, metal magnetic powder whose surface was slowly oxidized and whose differential thermal curve started changing temperature was 73°C was used. A videotape was produced by the process and process of

The obtained videotape was designated as Comparative Example Tape 7.

Comparative Example 8 Instead of the metal magnetic powder (1) in Table 1, a metal magnetic powder whose surface was slowly oxidized and whose differential thermal curve started changing at a temperature of 73°C was used, and sodium stearate (anionic dispersant) was used. A videotape was produced by the same treatment and steps as in Example 1, except that octadecylammonium chloride (cationic dispersant) was used instead.

The obtained videotape was designated as Comparative Example Tape 8.

Comparative Examples 9 to 15 Examples 1 to 15 except that lecithin (ampholytic dispersant) was used instead of sodium stearate (anionic dispersant).
Seven types of videotapes were produced by the same treatment and steps as in Example 7. For these seven types of tapes, the types of metal magnetic powder contained in the magnetic paint applied to the tapes (Table -
1, (1) to (7)), and were designated as Comparative Example Tapes 9 to 15, respectively.

Comparative Example 16 The magnetic powder used for producing magnetic paint was a metal magnetic powder whose differential thermal curve does not change up to at least 80°C (Table 1, NI
The same treatment and steps as in Example 1 were carried out except that octadecyl ammonium chloride (cationic dispersant) was used in place of sodium stearate (anionic dispersant) to be added to the ILI (ILI) mixed composition. , 12.
A 65ml videotape was made.

The obtained videotape was designated as Comparative Example Tape 16.

Example Tape 35 and Comparative Example Tape 1 obtained by Examples 1 to 35 and Comparative Examples 1 to 16 described above
Table 3 shows the results of measuring the tape performance of No. 6.

Tape performance was measured for still (still image) durability, abrasion resistance, and tack. These still durability,
Abrasion resistance and tackiness were expressed according to the following criteria.

(a) Still durability: Displayed as the time (in minutes) until the still image reproduction output decreases by 1 dB.

(b) Abrasion resistance: A 5 m long tape was repeatedly rubbed back and forth at a speed of 7 m/sec using a simulated head, and the tape orientation was determined visually and using a microscope. In other words, one with good wear resistance◎
Those that are continuous are marked with a circle, and those that are defective are marked with an X.

(c) Adhesion: Judgment was made based on the degree of sticking after being left for 24 hours under conditions of 80% humidity and 40°C.

Mark ○ for those in which no sticking occurs. Margin table below the occurrence of sticking. Example Tape 35 and Comparative Example Tape 9~
15 is a conventional metal magnetic powder (thermal curve is 20-75℃
Compared to tapes using magnetic powder (metal magnetic powder that changes with
Good still durability, abrasion resistance and adhesion.

On the other hand, even if the tape uses metal magnetic powder whose differential thermal curve does not change up to at least 80°C, the tape using a cationic dispersant (Comparative Example 6) has poor methyl durability and abrasion resistance. was found to be inferior.

In addition, products using conventional metal magnetic powder have low differential thermal curves in terms of still durability, abrasion resistance, and adhesion, even if anionic or nonionic dispersants are used. Both were found to be inferior to those containing metal magnetic powder, which did not change up to 80°C.

In addition, the magnetic paint used in producing Example Tape 35 and the magnetic paint used in producing Comparative Example Tape 15 were each applied to a glass plate using an applicator.
When it was applied to a thickness of 0 μm (when wet) and the state of dispersion was observed under a microscope, it was found that the magnetic paint used in Example Tape 35 was uniformly dispersed and had very few aggregates.

(g) Effects of the invention: As described above, the magnetic recording medium of the present invention containing a metal magnetic powder and an anionic or nonionic dispersant in which the differential thermal curve reaches at least 80°C in the magnetic layer has: (1) metal magnetic Since the powder is uniformly dispersed, there is no powder falling off, and a product with strong wear resistance can be obtained.

(2) Since a metal magnetic powder whose differential thermal curve does not change up to at least 80'C and an anionic or nonionic dispersant are used, oxidation stability is high and magnetic properties change little over time. Therefore, ■ Excellent still durability.

[Brief explanation of drawings]

Figure 1 is an electron microscope photograph of the surface of a conventional metal magnetic powder, and Figure 2 is an electron microscope photograph of the surface of a metal magnetic powder whose differential thermal curve does not change at least at 80°C1, used in the magnetic recording medium of the present invention. The photographs and FIG. 3 are cross-sectional views of metal magnetic powder whose powder surface is covered with a polymer compound, and FIG. 4 is a cross-sectional view of metal magnetic powder whose powder surface has been slowly oxidized. Patent applicant: Roku Konishi Photo Industry Co., Ltd. Figure 49 Figure 2 Figure 3 Figure 4 @ Procedural amendment (voluntary) October 11, 1981 Relationship with 11 patent applications No. 115680 Patent application Person 4 Location 1-26-2 L' Nishi-Shinjuku, Shinjuku-ku, Tokyo
+1 (4 cities) (” 27) Konishiroku Photo Industry Co., Ltd. B
Contents of the amendment Bessai Vno and 26 Solo (1) Specification page 25, line 6 “...Binder 10
0...'' is assumed to be "...magnetic powder 100...". (2) "...Binder 100..." in the second line from the bottom on page 25 of the specification is changed to "...Magnetic powder 100...". (3) "... Binder 100J" in the first line from the bottom of page 26 of the specification is "... Magnetic powder 100." Written amendment to the above procedure (voluntary) October 12, 1980 Patent Application No. 115680 3, Relationship to the case of the person making the amendment Patent applicant address 1-26-2 Nishi-Shinjuku, Shinjuku-ku, Tokyo M”i(
Name) (127) Konishiroku Photo Industry Co., Ltd. 8, Contents of correction 7I Kite Reno and X. 7. Statue. (1) At the bottom of page 25 of the specification, "... squaring" is changed to "...
・Square ratio” (2) Change "...Hagane..." in the bottom line of the second page of the specification to 1.
...copper..." (3) The description from page 25, line 13 to page 25, line 3 of the specification is deleted and the following description is added. □ For example, lecithin etc. can be used. (4) “These dispersants...” on page 25, line 4 of the specification
is referred to as "the dispersant and/or other dispersant...". (5) Delete the statement from line 8 to line 111 on page 25 of the detailed description. (6) The description on page 25, line 13 to line 155 of the specification is deleted. (Add the following sentence between line 2514 and line 155 of the specification. Instead of metal magnetic powder (1) in Table 1, the surface of metal magnetic powder whose differential thermal curve easily changes at room temperature. A silicone oil film is formed on the surface, and the temperature at which the differential thermal curve starts changing is 50℃.
A videotape was produced using the same treatment and steps as in Example 1, except that magnetic powder was used. This videotape was designated as Comparative Example Tape 1. Comparative example 2 Above

Claims (1)

[Claims] 1. A magnetic recording medium comprising, on a support, a magnetic layer containing a metal magnetic powder whose differential thermal curve does not change over at least 80''ct and an anionic or nonionic dispersant.