JPH04302820A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To enhance the stability of the magnetic recording medium with lapse of time and to provide the magnetic recording medium having excellent preservable stability. CONSTITUTION:The nitro deriv. of an org. acid having benzene skeletone is added into a magnetic coating material consisting essentially of magnetic powder and a binder at the time of forming a magnetic layer by using iron or ferromagnetic metallic particles constituted of the iron as the magnetic powder and applying the magnetic coating material consisting essentially of such magnetic powder and the binder on a nonmagnetic base. The nitro deriv. of the org. acid having the above-mentioned benzene skeleton is otherwise incorporated into the above-mentioned magnetic layer by using the ferromagnetic metallic particles previously subjected to a surface treatment in water or org. solvent contg. the nitro deriv. of the org. acid having the benzene skeleton as the above- mentioned magnetic powder. The oxidation resistance as the medium is improved and the deterioration of the magnetic characteristics with lapse of time is suppressed.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coating type magnetic recording medium using fine ferromagnetic metal particles as magnetic powder.

0002

[Prior Art] Generally, magnetic recording media such as magnetic tape are
It is manufactured by applying a magnetic paint consisting of magnetic powder and a binder onto a non-magnetic support and drying it. In recent years, in the field of magnetic recording, particularly in video tape recorders and the like, there has been a demand for even higher recording densities in order to achieve higher image quality. With this increase in recording density, iron or metallic magnetic materials mainly composed of iron have come to be used in place of iron oxide-based materials conventionally used as magnetic powders in magnetic recording media and the like. These ferromagnetic metal fine particles composed of iron or iron are iron oxide or iron oxyhydroxide, or iron oxide or oxyhydroxide containing metals other than iron such as Co, Ni, Mn, Cu, Zn, Ti, and V. Manufactured by reducing iron oxide etc. with hydrogen gas. These ferromagnetic metal fine particles have better magnetic properties than conventional iron oxide-based ferromagnetic particles.

However, the above-mentioned ferromagnetic metal fine particles have a high surface activity and are easily oxidized in the atmosphere, which may cause ignition in some cases. Such properties tend to become stronger as magnetic powder becomes finer as noise is reduced in magnetic recording media. For this reason, when the above-mentioned ferromagnetic metal fine particles are used as magnetic powder for a magnetic recording medium, during storage of the ferromagnetic metal fine particles,
Alternatively, during the process of forming a paint by combining it with a binder, organic solvent, etc., or after coating it on a non-magnetic support such as a polyester film to form a sheet, it is applied under specified conditions such as atmosphere, temperature, humidity, etc. During storage, oxidation progresses mainly due to the influence of oxygen, certain gases, moisture, etc., resulting in deterioration of magnetic properties such as saturation magnetization over time, resulting in storage stability problems. To solve this problem, in order to stabilize the surface of ferromagnetic metal fine particles, a method is generally used to form an oxide film on the particle surface using a liquid phase method or a gas phase method to passivate it. I've been exposed to it. In addition, methods have been taken in which ferromagnetic metal fine particles are coated with certain metal elements, surfactants, organic substances such as resins, and the like.

0004

[Problems to be Solved by the Invention] However, with the method of forming a passive oxide film or the method of covering with a certain metal element or organic substance, it is difficult to suppress oxidation of ferromagnetic metal particles and prevent deterioration of magnetic properties over time. It is difficult to say that it is necessarily sufficient to prevent such problems. Furthermore, depending on the treatment method, surface treatment itself may cause deterioration of magnetic properties or may cause a decrease in dispersibility when made into a paint. Therefore, the present invention has been proposed in view of these actual circumstances.
The purpose of the present invention is to improve the stability of a magnetic recording medium over time and provide a magnetic recording medium with excellent storage stability.

[0005]

[Means for Solving the Problems] As a result of intensive research, the present inventors found that the above object could not be achieved by including a nitro derivative of an organic acid having a benzene skeleton in the magnetic layer.
It was discovered that the oxidation resistance as a medium is improved and deterioration of magnetic properties over time can be suppressed, leading to the completion of the present invention. That is, the present invention provides a magnetic recording medium in which a magnetic layer mainly composed of magnetic powder and a binder is formed on a non-magnetic support, in which the magnetic layer contains a nitro derivative of an organic acid having a benzene skeleton. This is a characteristic feature. The magnetic powder used in the present invention includes:
Ferromagnetic metal materials such as Fe, Co, Ni, Fe-Co,
Fe-Ni, Fe-Co-Ni, Co-Ni, Fe-M
n-Zn, Fe-Ni-Zn, Fe-Co-Ni-Cr
, Fe-Co-Ni-P, Fe-Co-B, Fe-Co
-Ferromagnetic metal fine particles made of various ferromagnetic alloy materials mainly composed of Fe, Co, and Ni such as -Cr-B and Fe-Co-V.
Elements such as L, Si, Ti, Cr, Mn, Cu, Zn, Mg, and P may be added. The specific surface area of these ferromagnetic metal fine particles is arbitrary, but the specific surface area is 25 m
It is highly effective when applied to objects with a surface area of 2/g or more, especially 30 m2/g or more.

The magnetic recording medium of the present invention comprising such ferromagnetic metal fine particles contains a nitro derivative of an organic acid having a naphthalene skeleton in its magnetic layer. Although these compounds are added when forming a paint, it is also possible to use ferromagnetic metal fine particles that have been previously treated in water or an organic solvent containing these compounds. Further, these compounds may be used alone or in combination with different types of compounds. When the acid group is a hydroxyl group, examples of the organic acid include compounds shown in the following chemical formulas 1 to 17.

[Chemical formula 1]

[0007]

[Case 2]

[0008]

[Chemical formula 3]

[0009]

[C4]

0010

[C5]

[0011]

[C6]

0012

[C7]

[0013]

[Chemical formula 8]

[0014]

[Chemical formula 9]

[0015]

[Chemical formula 10]

[0016]

[Chemical formula 11]

[0017]

[Chemical formula 12]

[0018]

[Chemical formula 13]

[0019]

[Chemical formula 14]

[0020]

[Chemical formula 15]

[0021]

[Chemical formula 16]

[0022]

[Chemical formula 17]

When the functional group of the acid is a carboxyl group,
2-nitrobenzoic acid, 3-nitrobenzoic acid, 4-nitrobenzoic acid, 2,3-dinitrobenzoic acid, 2,4-dinitrobenzoic acid, 2,4-dinitrobenzoic acid, 2,3,4-
Trinitrobenzoic acid, 2,3,5-trinitrobenzoic acid, 3-nitrophthalic acid, 4-nitrophthalic acid, 3,4-
Dinitrophthalic acid, 4,5-dinitrophthalic acid, 3,5
-dinitrophthalic acid, 3,6-dinitrophthalic acid, 3,
Examples include compounds such as 4,5-trinitrophthalic acid, 3,4,6-trinitrophthalic acid, and 3,4,5,6-tetranitrophthalic acid. Further, these compounds may have an alkyl group such as a methyl group or ethyl, a halogen group such as fluorine or chlorine, an amino group, an acetyl group, etc., depending on the dispersibility required when forming a paint. As is well known, introducing an electron-withdrawing nitro group into catechol, benzoic acid, and phthalic acid improves the acidity of these organic acids, and the acidity of the parent organic acid can be adjusted depending on the number and position of substituents. This can be controlled, and organic acids with various acidities can be used depending on the surface properties of the magnetic powder.

[0024] As a method of using the above compound, when the above compound is deposited on the surface of ferromagnetic metal fine particles, the ferromagnetic metal fine particles are pretreated in water and an alcohol-based, ketone-based, or aromatic organic solvent. Alternatively, there is a method of adding it to the magnetic paint during the process of producing the magnetic paint. The amount of the compound used is 0.03 to 30 parts by weight, preferably 0.1 to 10 parts by weight, based on 100 parts by weight of the ferromagnetic metal fine particles.
Parts by weight. If the amount is outside the above range and the amount is small, effective oxidation resistance cannot be obtained, and if the amount is outside the above range and is large, the effect will not change and the excess amount will be wasted and the physical properties of the magnetic coating film of the magnetic recording medium will be affected. There is a risk of adverse effects. In the present invention, a magnetic recording medium is obtained by kneading the above-mentioned ferromagnetic metal fine particles and the above-mentioned compound together with a binder, an organic solvent, and various additives to form a paint, and coating the paint on a non-magnetic support. In this case, these organic acids may be used separately as a surface treatment agent for the ferromagnetic metal fine particles, or may be added when forming the paint. As the binder, organic solvent, and various additives, any of those used in ordinary magnetic recording media can be used. Further, in this case, the mixing ratio and the like are also set in accordance with the case of a normal magnetic recording medium.

Binders that can be used in the magnetic layer include:
Those with an average molecular weight of 10,000 to 200,000 are preferred;
For example, vinyl chloride-vinyl acetate copolymer, vinyl chloride-
Vinylidene chloride copolymer, vinyl chloride-vinyl acetate-polyvinyl alcohol copolymer, vinyl chloride-acrylonitrile copolymer, polyurethane resin, butadiene-acrylonitrile copolymer, polyamide resin, polyvinyl butyral, cellulose derivative (cellulose acetate butyrate, cellulose diacetate, cellulose triacetate, cellulose propionate, nitrocellulose, etc.), styrene-butadiene copolymer, polyester resin, various synthetic rubbers, phenolic resin, epoxy resin, urea resin, melamine resin, phenoxy resin, silicone resin , acrylic resins, mixtures of high molecular weight polyester resins and isocyanate prepolymers, mixtures of polyester polyols and polyisocyanates, urea formaldehyde resins, mixtures of low molecular weight glycols, high molecular weight diols and isocyanates, and mixtures thereof. Ru. These binders are -SO3 M, -C
OOM, -PO(OM')2 (where M is hydrogen or
Alkali metals such as lithium, potassium, sodium, M
' is preferably a resin containing a hydrophilic polar group such as hydrogen, an alkali metal such as lithium, potassium, or sodium, or a hydrocarbon residue). In other words, such resins have improved compatibility with magnetic powder due to the polar groups in their molecules,
This suppresses agglomeration of the magnetic powders, thereby increasing the dispersion stability of the magnetic powders and, in turn, improving the durability of the medium. Among the binders mentioned above, vinyl chloride-based copolymers are vinyl chloride monomers, copolymerizable monomers containing sulfonic acid or alkali phosphate salts, and various other copolymerizable monomers as necessary. It can be easily obtained by copolymerization. This makes it possible to arbitrarily control the polarity of the copolymer and improve the dispersion stability of the particles.

A dispersant is used in the magnetic paint used to form the magnetic layer, and additives such as a lubricant, an abrasive, a matting agent, an antistatic agent, etc. may be included as necessary. Dispersants used in the present invention include phosphoric acid esters, amine compounds, alkyl sulfates, fatty acid amides, higher alcohols, polyethylene oxides, sulfosuccinic acids, sulfosuccinic esters, known surfactants, and salts thereof. , and also negative organic acids (e.g. -COO
It is also possible to use salts of polymeric dispersants having H). These dispersants may be used alone or in combination of two or more. In addition, as lubricants, silicone oil, graphite, carbon black graphite polymer, molybdenum disulfide, tungsten disulfide,
Lauric acid, myristic acid, fatty acids having 12 to 16 carbon atoms, and the total number of carbon atoms in the fatty acids is 21
Fatty acid esters consisting of ~23 monohydric alcohols can also be used. These lubricants are usually added in an amount of 0.2 to 20 parts by weight per 100 parts by weight of the binder. As the abrasive, commonly used materials such as fused alumina, various types of alumina such as α-alumina, silicon carbide, chromium oxide, corundum, artificial corundum, artificial diamond, garnet, emery, etc. are used. These abrasives have an average particle diameter of 0.05 to 5 μm, particularly preferably 0.1 to 2 μm. These abrasives are usually added in an amount of 1 to 20 parts by weight per 100 parts by weight of the binder. As the matting agent, organic powder or inorganic powder can be used individually or in combination. As the organic powder used in the present invention, acrylic styrene resin powder, benzoguanamine resin powder, melamine resin powder, and phthalocyanine pigment are preferable, but polyolefin resin powder, polyester resin powder, polyamide resin powder, and polyimide resin powder are preferable. Resin powder, polyfluoroethylene resin powder, etc. can also be used, and inorganic powders include silicon oxide, titanium oxide, aluminum oxide, calcium carbonate, barium sulfate, zinc oxide, tin oxide, chromium oxide, silicon carbide, iron oxide, talc, Examples include kaolin, calcium sulfate, boron nitride, zinc fluoride, and molybdenum dioxide. Antistatic agents include carbon black, graphite, conductive powders such as tin oxide and antimony monoxide compounds, titanium oxide and tin monoxide and antimony monoxide compounds, natural surfactants such as saponin, alkylene oxides, and glycerin. nonionic surfactants such as glycidol-based, higher alkylamines, quaternary ammonium salts, pyridine, other heterocycles, cationic surfactants such as phosphonium or sulfonium, carboxylic acids, sulfonic acids, phosphoric acids, and sulfuric esters. Examples include anionic surfactants containing acidic groups, such as amino acids, amino sulfonic acids, and amphoteric surfactants such as sulfuric acid or phosphoric acid esters of amino alcohols.

[0027] As the solvent to be added to the magnetic paint or the diluting solvent when applying the magnetic paint, ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone, alcohols such as methanol, ethanol, propanol, and butanol, Esters such as methyl acetate, ethyl acetate, butyl acetate, ethyl lactate, ethylene glycol monoacetate, ethers such as glycol dimethyl ether, glycol monoethyl ether, dioxane, tetrahydrofuran, aromatic hydrocarbons such as benzene, toluene, xylene, methylene Chloride, ethylene chloride, carbon tetrachloride, chloroform,
Halogenated hydrocarbons such as dichlorobenzene can be used. Examples of non-magnetic supports include polyesters such as polyethylene terephthalate and polyethylene-2,6-naphthalate, polyolefins such as polypropylene, cellulose derivatives such as cellulose triacetate and cellulose diacetate, and plastics such as polyamide and polycarbonate. However, metals such as copper, aluminum, and zinc, glass, and ceramics such as boron nitride and silicon carbide can also be used.

The thickness of these non-magnetic supports is as follows:
In the case of a sheet, the thickness is approximately 3 to 100 μm, preferably 5 μm.
~50μm, and 30μm for disks and cards
m to about 10 mm, and in the case of a drum shape, it is used in a cylindrical shape, and its shape is determined depending on the recorder used. An intermediate layer for improving adhesion may be provided between the nonmagnetic support and the magnetic layer. Coating methods for forming the magnetic layer on the non-magnetic support include air doctor coating, blade coating, air knife coating, squeeze coating, impregnation coating, reverse roll coating, transfer roll coating, gravure coating, kiss coating, and cast coating. , spray coating, extrusion coating, etc. can be used, but are not limited to these. When constructing a magnetic layer on a non-magnetic support using these coating methods, there are two methods: one is to apply and dry one layer at a time, and the other is to apply the next layer one after another on top of a wet layer that has not been dried. However, either method can be adopted in manufacturing the magnetic recording medium of the present invention. By such a method, the magnetic layer coated on the nonmagnetic support is optionally subjected to a treatment for orienting the ferromagnetic metal fine particles in the layer, and then the formed magnetic layer is dried. In this case, the orientation magnetic field is about 500 to 5000 Gauss in alternating current or direct current, the drying temperature is about 50 to 120°C, and the drying time is about 0.1 to 10 minutes. Further, the magnetic recording medium of the present invention is manufactured by subjecting it to a surface smoothing treatment or cutting it into a desired shape, if necessary.

[0029]

EXAMPLES The present invention will be explained below with reference to specific examples, but it goes without saying that the present invention is not limited to these examples. Example 1 An example will be shown below. All the compounds used here were synthesized, and their structures were confirmed by nuclear magnetic resonance spectra and infrared absorption spectra. Acicular metal iron magnetic fine particles (specific surface area 53.9 m2 /g, coercive force Hc=
The study was conducted using 1590 Oe, saturation magnetization σs = 120 emu/g, average major axis length 0.3 μm, and acicular ratio 8 to 10). 2.0 x 10-3 m of 4-nitrocatechol
5 parts by weight of the metal iron magnetic fine particles were dispersed in 10 parts by weight of an ol/1 ethanol solution, irradiated with ultrasonic waves for about 30 minutes, and then allowed to stand for about 2 hours. The metal iron magnetic fine particles were filtered, washed repeatedly with ethanol, and then vacuum dried to obtain treated magnetic fine particles.

Treated magnetic fine particles
100 parts by weight Vinyl chloride vinyl acetate copolymer 10 parts by weight Polyurethane resin
10 parts by weight carbon
3 parts by weight aluminum oxide
2 parts by weight methyl ethyl ketone
100 parts by weight toluene

100 parts by weight cyclohexanone
A magnetic paint having the above composition was prepared in an amount of 50 parts by weight, and was coated on a 9 μm polyester base film to prepare a magnetic tape.

The magnetic tape thus obtained was kept for one week under conditions of 90% humidity and 60° C., and the deterioration of the magnetic properties over time was investigated by comparing with the initial value before storage. The results are shown in Table 1. For comparison, a magnetic tape was prepared by replacing the treated magnetic fine particles in the magnetic paint with untreated ferromagnetic metal fine particles, and the results are also reported.

[Table 1]

Example 2 A magnetic paint having the following composition was prepared using the metal iron magnetic fine particles prepared in Example 1, and a magnetic tape was prepared in the same manner as in Example 1. In this case, 4-nitrocatechol is kneaded as part of the composition. Metallic iron magnetic particles
100 parts by weight 4-nitrocatechol
3 parts by weight vinyl chloride vinyl acetate copolymer 10
Weight part polyurethane resin
10 parts by weight carbon

3 parts by weight aluminum oxide
2 parts by weight methyl ethyl ketone 1
00 parts by weight toluene
100 parts by weight cyclohexanone
Example 1 Regarding the magnetic tape obtained by 50 parts by weight
Deterioration over time was investigated in the same manner as above. The results are shown in Table 2.

[Table 2]

Example 3 In this example, acicular metal iron magnetic fine particles (specific surface area 53.9 m2 /g, coercive force Hc = 15
90 Oe, saturation magnetization σs=120 emu/g, average major axis length 0.3 μm, and acicular ratio 8 to 10). That is, 4,5-dinitrocatechol 2.0 x 10
5 parts by weight of the metal iron magnetic fine particles were dispersed in 100 parts by weight of -3 mol/l ethanol solution, irradiated with ultrasonic waves for about 30 minutes, and then allowed to stand for about 2 hours. The metal iron magnetic fine particles were filtered, washed repeatedly with ethanol, and then vacuum dried to obtain treated magnetic fine particles. treated magnetic particles
100 parts by weight Vinyl chloride vinyl acetate copolymer 10 parts by weight Polyurethane resin
10 parts by weight carbon
3 parts by weight aluminum oxide
2 parts by weight methyl ethyl ketone
100 parts by weight toluene

100 parts by weight cyclohexanone
A magnetic paint having the above composition was prepared in an amount of 50 parts by weight, and was coated on a 9 μm polyester base film to prepare a magnetic tape. Regarding the obtained magnetic tape, deterioration over time was examined in the same manner as in Example 1. The results are shown in Table 3.

[Table 3]

Example 4 A magnetic paint having the following composition was prepared using the metal iron magnetic fine particles of Example 3, and a magnetic tape was prepared in the same manner as in Example 1. Metallic iron magnetic particles
100 parts by weight 4,5-dinitrocatechol
3 parts by weight Vinyl chloride vinyl acetate copolymer 10 parts by weight Polyurethane resin
10 parts by weight carbon

3 parts by weight aluminum oxide
2 parts by weight Methyl ethyl ketone 100 parts by weight Toluene
100 parts by weight cyclohexanone 5
Regarding the obtained magnetic tape (0 parts by weight), deterioration over time was examined in the same manner as in Example 1. The results are shown in Table 4.

[Table 4]

Example 5 In this example, acicular metal iron magnetic fine particles (specific surface area 53.9 m2/g, coercive force Hc=15
90 Oe, saturation magnetization σs=120 emu/g, average major axis length 0.3 μm, and acicular ratio 8 to 10). That is, 3,4-dinitrobenzoic acid 2.0 x 10-3
5 parts by weight of the metal iron magnetic fine particles were dispersed in 100 parts by weight of a mol/l ethanol solution, irradiated with ultrasonic waves for about 30 minutes, and then allowed to stand for about 2 hours. The metal iron magnetic fine particles were filtered, washed repeatedly with ethanol, and then vacuum dried to obtain treated magnetic fine particles. treated magnetic particles
100 parts by weight Vinyl chloride vinyl acetate copolymer 10 parts by weight Polyurethane resin
10 parts by weight carbon
3 parts by weight aluminum oxide
2 parts by weight methyl ethyl ketone
100 parts by weight toluene

100 parts by weight cyclohexanone
A magnetic paint having the above composition was prepared in an amount of 50 parts by weight, and was coated on a 9 μm polyester base film to prepare a magnetic tape. Regarding the obtained magnetic tape, deterioration over time was examined in the same manner as in Example 1. The results are shown in Table 5.

[Table 5]

Example 6 A magnetic paint having the following composition was prepared using the metal iron magnetic fine particles of Example 5, and a magnetic tape was prepared in the same manner as in Example 1. Metallic iron magnetic particles
100 parts by weight 3,4-dinitrobenzoic acid
3 parts by weight Vinyl chloride vinyl acetate copolymer 10 parts by weight Polyurethane resin
10 parts by weight carbon

3 parts by weight aluminum oxide
2 parts by weight methyl ethyl ketone 100
Part by weight toluene
100 parts by weight cyclohexanone
Regarding the magnetic tape obtained in an amount of 50 parts by weight, deterioration over time was examined in the same manner as in Example 1. The results are shown in Table 6.

[Table 6]

Example 7 In this example, acicular metal iron magnetic fine particles (specific surface area 53.9 m2 /g, coercive force Hc = 15
90 Oe, saturation magnetization σs=120 emu/g, average major axis length 0.3 μm, and acicular ratio 8 to 10). That is, 4,5-dinitrobenzoic acid 2.0 x 10-
5 parts by weight of the metal iron magnetic fine particles were dispersed in 100 parts by weight of a 3 mol/l etal solution, irradiated with ultrasonic waves for about 30 minutes, and then allowed to stand for about 2 hours. The metal iron magnetic fine particles were filtered, washed repeatedly with ethanol, and then vacuum dried to obtain treated magnetic fine particles. treated magnetic particles
100 parts by weight Vinyl chloride vinyl acetate copolymer 10 parts by weight Polyurethane resin
10 parts by weight carbon
3 parts by weight aluminum oxide
2 parts by weight methyl ethyl ketone
100 parts by weight toluene
100 parts by weight cyclohexanone
A magnetic paint having the above composition was prepared in an amount of 50 parts by weight, and was coated on a 9 μm polyester base film to prepare a magnetic tape. Regarding the obtained magnetic tape, deterioration over time was examined in the same manner as in Example 1. The results are shown in Table 7.

[Table 7]

Example 8 A magnetic paint having the following composition was prepared using the metal iron magnetic fine particles of Example 7, and a magnetic tape was prepared in the same manner as in Example 1. Metallic iron magnetic particles
100 parts by weight 4,5-dinitrobenzoic acid
3 parts by weight Vinyl chloride vinyl acetate copolymer 10 parts by weight Polyurethane resin
10 parts by weight carbon

3 parts by weight aluminum oxide
2 parts by weight methyl ethyl ketone 100
Part by weight toluene
100 parts by weight cyclohexanone
Regarding the magnetic tape obtained in an amount of 50 parts by weight, deterioration over time was examined in the same manner as in Example 1. The results are shown in Table 8.

[Table 8]

[0039]

[Effects of the Invention] As is clear from Tables 1 to 8, the magnetic tape treated with a nitro compound of an organic acid having a benzene skeleton or mixed when forming into a paint is more effective than when untreated magnetic powder is used. , the decrease in residual magnetic flux density and coercive force is extremely small, and the squareness ratio is maintained at its initial value. Therefore, in the magnetic recording medium of the present invention, the stability of magnetic properties over time and storage stability are significantly improved.

Claims (1)

[Claims] 1. A magnetic recording medium comprising a magnetic layer mainly composed of magnetic powder and a binder formed on a non-magnetic support, wherein the magnetic layer contains a nitro derivative of an organic acid having a benzene skeleton. Features of magnetic recording media.