JPH1166544A - Magnetic recording media - Google Patents

Abstract

(57) [Abstract] [Problem] The surface electric resistance is low, and it is difficult for dust and dirt to adhere.
An object of the present invention is to provide a magnetic recording medium having excellent durability, running properties, and recording / reproducing characteristics. A magnetic recording medium comprising a support and a magnetic layer provided on the support, wherein the magnetic layer contains granular, non-magnetic Mn-containing iron oxide particles in the magnetic layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a magnetic recording medium.

[0002]

2. Description of the Related Art For example, a coating type magnetic recording medium such as a magnetic tape is prepared by kneading a magnetic powder, a binder resin, other various additives and a solvent with a magnetic coating material, and mixing a magnetic paint with a base film such as a polyester film. In general, those having a magnetic layer formed by coating on one surface side of a (body). If necessary, a coating obtained by kneading carbon black, a binder resin, other various additives and a solvent is applied to the other surface of the support (the side opposite to the side on which the magnetic layer is provided). By applying, a so-called back layer is provided. Further, there is also known a structure in which a so-called intermediate layer is provided between a magnetic layer and a support.

[0003] Various proposals have been made for components of the magnetic layer, the back layer, and the intermediate layer in these magnetic recording media since ancient times. That is, various proposals (for example, Japanese Patent Application Laid-Open Nos. 50-30503 and 57-88) are made from the viewpoint of improving running properties, durability, and electromagnetic conversion characteristics.
529, JP-A-59-14124, JP-A-59-92436, JP-A-60-50619, JP-A-62-295216, JP-A-60-8
No. 5424, JP-A-60-179929, JP-A-60-179934, JP-A-62-27592.
No. 9, JP-A-58-199437, JP-A-58-199437
No. 8-200429).

[0004]

However, further improvement in running properties and durability has been required. In particular, a reduction in surface electrical resistance is required, and dust and dirt are unlikely to adhere,
Further, further improvement in recording / reproducing characteristics was required. Accordingly, an object of the present invention is to provide a magnetic recording medium which has low surface electric resistance, hardly adheres dust and dirt, and has excellent durability, running properties, and recording / reproducing characteristics.

[0005]

SUMMARY OF THE INVENTION The object of the present invention is to provide a magnetic recording medium comprising a support and a magnetic layer provided on the support, wherein a granular, non-magnetic Mn-containing iron oxide particle is prepared. The problem is solved by a magnetic recording medium characterized by being contained in a magnetic layer.

[0006] In particular, in a magnetic recording medium comprising a support and a magnetic layer provided on the support, the magnetic recording medium has a granular shape.
Nonmagnetic Mn-containing iron oxide particles are contained in the magnetic layer in a ratio of 0.5 to 130 parts by weight (preferably 5 to 100 parts by weight) based on 100 parts by weight of the binder resin in the magnetic layer. The problem is solved by the characteristic magnetic recording medium.

In a magnetic recording medium comprising a support, a magnetic layer provided on one side of the support, and a back layer provided on the other side of the support, a granular, non-magnetic The Mn-containing iron oxide particles are contained in the back layer. Especially,
A support, a magnetic layer provided on one surface side of the support,
In a magnetic recording medium comprising a back layer provided on the other surface side of the support, particulate, non-magnetic Mn-containing iron oxide particles are added in an amount of 0.1 to 100 parts by weight of the binder resin in the back layer. The problem is solved by a magnetic recording medium characterized in that the back layer contains 1 to 20 parts by weight (preferably 1 to 15 parts by weight).

In a magnetic recording medium comprising a support, a magnetic layer provided on one side of the support, and an intermediate layer provided between the support and the magnetic layer, a magnetic recording medium comprising:
The problem is solved by a magnetic recording medium characterized in that non-magnetic Mn-containing iron oxide particles are contained in the intermediate layer. In particular, in a magnetic recording medium including a support, a magnetic layer provided on one surface side of the support, and an intermediate layer provided between the support and the magnetic layer, the magnetic recording medium is granular, non-magnetic. Mn
Containing iron oxide particles, the binder resin 100 in the intermediate layer.
0.5 to 130 parts by weight (preferably 5 to 130 parts by weight)
(100 parts by weight) in the intermediate layer.

That is, by containing granular, nonmagnetic Mn-containing iron oxide particles in at least one of a magnetic layer, an intermediate layer, and a back layer, the surface electric resistance is reduced.
Dust and dust are less likely to adhere. As a result, durability and running properties are improved. Then, the dropout is small and the recording / reproducing characteristics are excellent. In addition, granular, non-magnetic Mn
When containing iron oxide particles in the magnetic layer,
Clogging and dropout hardly occur in the magnetic head, and furthermore, the running durability is improved. When the magnetic head is included in the back layer, the running durability is particularly improved, and the magnetic head is included in the intermediate layer. In particular, dropout hardly occurred and running durability improved.

In the present invention, the Mn-containing iron oxide particles are granular. The shape that this granularity means is spherical or
It has a polyhedral shape such as a cubic shape. Therefore, it is different from a so-called needle-shaped one. The Mn-containing iron oxide particles have an average particle size of 0.05 to 0.5 μm (particularly, 0.1 to 0.3 μm).
Are preferred. That is, if it is too small, less than 0.05 μm, the dispersibility decreases, the electromagnetic conversion characteristics decrease,
Furthermore, the polishing characteristics are hardly improved, and the magnetic head tends to be clogged. Conversely, if the size exceeds 0.5 μm, the surface properties are reduced, and the electromagnetic conversion characteristics are likely to be reduced. This is because the.

The Mn-containing iron oxide particles preferably have a specific surface area of ² to 15 m ² / g (particularly, ^{2 to} 12 m ² / g). That is, when the specific surface area is less than 2 m ² / g, the dispersibility tends to decrease and the electromagnetic conversion characteristics tend to decrease. Conversely, when the specific surface area exceeds 15 m ² / g, the dispersibility decreases, This is because there was a tendency for the conversion characteristics to decrease.

The Mn-containing iron oxide particles preferably have a water content of 5% or less (particularly 3% or less). That is, when the water content exceeds 5%, the dispersibility tends to decrease, and the electromagnetic conversion characteristics tend to decrease.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION A magnetic recording medium according to the present invention is a magnetic recording medium comprising a support and a magnetic layer provided on the support. Is contained in the magnetic layer. In particular, in a magnetic recording medium comprising a support and a magnetic layer provided on the support, granular, non-magnetic Mn-containing iron oxide particles are added to the binder resin in the magnetic layer by 100 parts by weight. 0.5 to 130 parts by weight (preferably 5 to 100 parts by weight) in the magnetic layer. Further, in a magnetic recording medium comprising a support, a magnetic layer provided on one surface side of the support, and a back layer provided on the other surface side of the support, the magnetic recording medium contains granular, non-magnetic Mn-containing material. Iron oxide particles are contained in the back layer. In particular, in a magnetic recording medium comprising a support, a magnetic layer provided on one side of the support, and a back layer provided on the other side of the support, a granular, nonmagnetic Mn-containing 0.1-20 parts by weight (preferably 1-15 parts by weight) of iron oxide particles with respect to 100 parts by weight of the binder resin in the back layer.
In the back layer. Further, in a magnetic recording medium comprising a support, a magnetic layer provided on one surface side of the support, and an intermediate layer provided between the support and the magnetic layer, a granular, non-magnetic Mn-containing iron oxide particles are contained in the intermediate layer. In particular, in a magnetic recording medium comprising a support, a magnetic layer provided on one surface side of the support, and an intermediate layer provided between the support and the magnetic layer, a granular, non-magnetic 0.5 to 130 parts by weight (preferably 5 to 100 parts by weight) of the Mn-containing iron oxide particles with respect to 100 parts by weight of the binder resin in the intermediate layer.
(Parts by weight) in the intermediate layer. In addition, a granular, non-magnetic Mn-containing iron oxide particle is formed by mixing two or more magnetic layers, a back layer, and an intermediate layer, for example, a magnetic layer and a back layer, a magnetic layer and an intermediate layer, or a back layer and an intermediate layer, or a magnetic layer. It is contained in the layer, the back layer and the intermediate layer. The Mn-containing iron oxide particles have an average particle size of 0.05 to 0.5 μm (particularly,
0.1-0.3 μm). The Mn-containing iron oxide particles have a specific surface area of ² to 15 m ² / g (further, ² to 12 m ² / g).
² / g. In particular, 3 to 10 m ² / g. ). The Mn-containing iron oxide particles have a water content of 5% or less (in particular, 3%
Below). In addition, p of the Mn-containing iron oxide particles
H is 2 to 11 (particularly, 3 to 10). Also, the above Mn
The tap density of the contained iron oxide particles is 1 to 3 g / ml.
The apparent density is 0.3 to 0.8 g / ml.

Hereinafter, the present invention will be described in detail. The support used in the magnetic recording medium of the present invention is non-magnetic. Examples of such a support include polyesters such as polyeletin terephthalate (PET) and polyethylene-2,6-naphthalate, polyolefins such as polyethylene and polypropylene, cellulose triacetate, cellulose diacetate, cellulose acetate butyrate, and cellulose. Cellulose derivatives such as acetate propionate, polyvinyl chloride, vinyl resins such as polyvinylidene chloride, polycarbonate, polyimide,
Plastics such as polyamideimide, paper, baryta or papers such as paper coated or laminated with α-polyolefins having 2 to 10 carbon atoms such as polyethylene, polypropylene, ethylene-butene copolymer and the like can also be used. In addition, metals such as Al alloys and ceramics such as glass and porcelain are also used. These nonmagnetic supports may be transparent or opaque depending on the purpose of use. The thickness of the support varies depending on the application, but is 3 to 15 μm.
It is.

A magnetic layer is provided on one side of the support.
That is, a magnetic layer having a thickness of 0.1 to 3.0 μm after drying is provided by applying a magnetic paint on one surface of the support. Here, the thickness of the magnetic layer after drying is 0.1 to
The reason for setting the thickness to 3.0 μm is that if the thickness is too thin, uniform coating is difficult, the output also decreases, the rigidity also decreases, and the head touch decreases.
This is because the thickness loss is increased and the output in a high frequency range is reduced, and the overwrite characteristics are reduced. In addition, more preferably, the thickness after drying is 0.15 to 2.5 μm.

As the magnetic powder contained in the magnetic layer, a known magnetic powder is appropriately used. For example, ferromagnetic metal (including alloy) powder is used. The ferromagnetic metal powder has a metal content of 75% by weight or more, and 80% by weight or more of the metal content is at least one type of ferromagnetic metal (for example, Fe, Co, Ni, Fe—Co, Fe—Ni, Co).
-Ni, Fe-Co-Ni), and 20% by weight or less of metal content, preferably 0.5 to 5% by weight of Al,
Si, S, Sc, Ti, V, Cr, Mn, Cu, Zn,
Y, Mo, Rh, Pd, Ag, Sn, Sb, Te, B
a, Ta, W, Re, Au, Hy, Pb, Bi, La,
It may have a composition such as Ce, Pr, Nd, B, and P. This ferromagnetic metal powder has a major axis of 0.05 to
Preferably, the particles are 0.2 μm. Its needle ratio is 3
It is preferably from 10 to 10. The coercive force is 1500-2
Those which are 500 Oe are preferred. In addition to the above magnetic powder, a hexagonal ferrite magnetic powder can also be used. This ferrite magnetic powder has a plate diameter of 0.02 to 0.02.
It is preferably 0.1 μm. Its plate ratio is 2
It is preferably from 10 to 10. The coercive force is 1500-3
000 Oe is preferred. In addition, an oxide-based magnetic powder can be used. By using the magnetic powder having the above characteristics, the coercive force Hc in the longitudinal direction becomes 1
300-3000 Oe, saturation magnetic flux density Bs is 2000-
A magnetic layer having 5000 G and a squareness ratio Sq of 0.7 to 0.95 is obtained.

The magnetic powder is subjected to a surface treatment, if necessary, to improve the dispersibility of the magnetic powder in the magnetic paint. For example, "Characterization of Powder
Surfaces (Academic Press) ". Further, a silane coupling treatment, a titanium coupling treatment, an alumina coupling treatment, or the like can be performed. Also, resin coating can be performed.

The coating type magnetic layer may contain an abrasive other than the above-mentioned Mn iron oxide powder. Examples of the abrasive include fused alumina, silicon carbide, chromium oxide (Cr ₂ O ₃ ), corundum, artificial corundum, diamond, artificial diamond, garnet, emery (main components: conradum and magnetite). Of course, it is not limited only to these. These abrasives have a Mohs hardness of 5 or more and an average particle diameter of 0.05 to 5 μm, and particularly preferably 0.1 to 2 μm. These abrasives are added in a range of 0.5 to 15 parts by weight based on 100 parts by weight of the magnetic powder.

In the coating type magnetic layer, in addition to the above components,
The additives usually used in this field include antistatic agents, lubricants, dispersants and the like. Examples of antistatic agents include conductive fine powders such as carbon black and titanium monoxide, natural surfactants such as saponin, nonionic surfactants such as alkylene oxide, glycerin and glycidol, higher alkylamines, and quaternary. Ammonium salts,
Pyridine and other heterocycles, cationic surfactants such as phosphonium or sulfonium, carboxylic acids, sulfonic acids, phosphoric acids, sulfate groups, anionic surfactants containing acidic groups such as phosphate groups, amino acids, aminosulfonic acids, And amphoteric activators such as sulfuric acid or phosphoric acid esters of amino alcohol. Such an antistatic agent is added in an amount of 0.01 to 10 parts by weight based on 100 parts by weight of the magnetic powder. The above surfactants may be added alone or as a mixture. Some of them are used as antistatic agents, but sometimes they are used for other purposes such as dispersion, improvement of magnetic properties, improvement of lubricity, and application aids.

As the lubricant, for example, dialkylpolysiloxane (alkyl group having 1 to 5 carbon atoms), dialkoxypolysiloxane (alkoxy group has 1 to 4 carbon atoms), monoalkylmonoalkoxypolysiloxane (alkyl group has 1 to 5 carbon atoms, the alkoxy group has 1 to 4 carbon atoms),
Silicone oils such as phenylpolysiloxane and fluoroalkylpolysiloxane (the alkyl group has 1 to 5 carbon atoms); conductive fine powders such as graphite; inorganic fine powders such as molybdenum disulfide and tungsten disulfide; polyethylene, polypropylene, and polyethylene -Vinyl chloride copolymer, plastic fine powder such as polytetrafluoroethylene, α-olefin polymer, unsaturated aliphatic hydrocarbon liquid at room temperature, monobasic aliphatic having 12 to 20 carbon atoms and 3 carbon atoms Fatty acid esters composed of up to 12 monohydric alcohols, fluorocarbons and the like. Some of the following dispersants exhibit a function as a lubricant, and these may be used. These lubricants are added in the range of 0.1 to 15 parts by weight based on 100 parts by weight of the magnetic powder.

Examples of the dispersant include fatty acids having 12 to 18 carbon atoms (R ₁ COOH, R ₁ is an alkyl or alkenyl group having 11 to 17 carbon atoms) and alkali metals of the above fatty acids (Li, Na, K, etc.). ) Or alkaline earth metals (Mg,
Ca, Ba, etc.), a fluorine-containing compound of the fatty acid ester, an amide of the fatty acid,
Examples thereof include polyalkylene oxide alkyl phosphates, lecithin, and trialkyl polyolefin oxy quaternary ammonium salts (alkyl has 1 to 5 carbon atoms, and olefins include ethylene and propylene). In addition, there are also higher alcohols having 12 or more carbon atoms, sulfates, and the like. These dispersants are used in an amount of 1 to 100 parts by weight of the magnetic powder.
It can be added in a range of 0 parts by weight or less.

Further, in addition to the above components, a rust inhibitor and a fungicide may be added. As the fungicide, for example, phosphoric acid, sulfamide, guanidine, pyridine, amine, urea, zinc chromate, calcium chromate, strontium chromate, and the like can be used, and in particular, dicyclohexylamine nitrite, cyclohexylamine chromate, diisopropylamine nitrite, diethanolamine Phosphate, cyclohexyl ammonium carbonate, hexamethylene diamine carbonate,
The use of a vaporizable rust inhibitor (an inorganic acid salt or an organic acid salt of an amine, an amide or an imide) such as propylene diamine stearate, guanidine carbonate, triethanolamine nitrite, and morpholine stearate improves the rust prevention effect.

Examples of fungicides include saltyl anilide, bis (tributyltin) oxide, mercury phenyloleate, copper naphthenate, zinc naphthenate, mercury naphthenate, pentachlorophenol, trichlorophenol,
Examples thereof include p-dinitrophenol, sorbic acid, butyl p-oxybenzoate, and dihydroacetoic acid. A binder resin is used to form the coating type magnetic layer.
In particular, the binder resin is used in an amount of 5 to 100 parts by weight, especially 5 to 70 parts by weight based on 100 parts by weight of the magnetic powder. For example, a thermoplastic resin is used. In particular,
Polyvinyl chloride, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinylidene chloride copolymer, vinyl chloride-acrylonitrile copolymer, acrylate-acrylonitrile copolymer, acrylate-vinylidene chloride copolymer, acrylic Acid ester-styrene copolymer,
Methacrylate-acrylonitrile copolymer, methacrylate-vinylidene chloride copolymer, methacrylate-styrene copolymer, urethane elastomer, polyvinyl fluoride, vinylidene chloride-acrylonitrile copolymer, 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 rubber thermoplastics Resins (polybutadiene, polychloroprene, polyisoprene, styrene-butadiene copolymer, etc.) and mixtures thereof are used. Alternatively, a thermosetting resin or a reactive resin can be used. For example, phenol-formalin-novolat resin, phenol-formalin-resol resin, phenol-furfural resin, xylene-formaldehyde resin, urea resin,
Melamine resin, drying oil-modified alkyd resin, phenolic resin-modified alkyd resin, maleic acid resin-modified alkyd resin, unsaturated polyester resin, epoxy resin and curing agent (polyamine, acid anhydride, polyamide resin, etc.),
Terminal isocyanate polyester moisture-curable resin, terminal isocyanate polyether moisture-curable resin, polyisocyanate prepolymer (compound having three or more isocyanate groups in one molecule obtained by reacting diisocyanate and low molecular weight triol, diisocyanate Trimer and tetramer), polyisocyanate prepolymer and resin having active hydrogen (polyester polyol, polyether polyol, acrylic acid copolymer, maleic acid copolymer, 2-hydroxyethyl methacrylate copolymer, parahydroxystyrene copolymer) Such),
And mixtures thereof.

In the present invention, the number of magnetic layers is not limited to one, but may be two or more. On the other side of the support, a so-called back layer is provided. The back layer is generally
Non-magnetic. However, the magnetic recording medium may have such a magnetic property that it cannot be used for recording and reproduction. For example, the back layer may contain a magnetic powder having a low coercive force (for example, spherical magnetite having a diameter of 0.005 to 0.2 μm). The back layer is provided with a thickness after drying of 0.1 to 5 μm (particularly 0.2 to 3 μm) by applying a coating material having a desired component on the other surface of the support. Here, the thickness of the back layer after drying is 0.1 to 5 μm.
m (especially 0.2 to 3 μm) is that if the thickness is less than 0.1 μm, uniform coating is difficult, the Young's modulus of the back layer is small, and appropriate rigidity cannot be provided. This is because the touch is reduced.

The back layer contains carbon black. The content of carbon black is 50 to 200 parts by weight, particularly 80 to 150 parts by weight, based on 100 parts by weight of the binder resin in the back layer. Carbon black has, for example, a primary particle size of 5 to 150 nm, a BET specific surface area of 12 to 1000 m ² / g, and a DBP oil absorption of 40 to 3.
00 ml / 100 g of carbon black.

In addition, the same lubricants and dispersants as described for the magnetic layer may be used, if necessary. Since the back layer is of a coating type, it contains the same binder resin as described for the magnetic layer. A non-magnetic or magnetic intermediate layer is provided between the support and the magnetic layer, if necessary. Since the intermediate layer is of a coating type, it contains the same binder resin as described for the magnetic layer.

When a non-magnetic intermediate layer is provided, the intermediate layer contains a non-magnetic powder and a binder resin. The non-magnetic powder may be any. For example,
Metal oxide powders such as titanium oxide, zinc oxide, calcium oxide, magnesium oxide, cerium oxide, tin dioxide, alumina, non-magnetic chromium oxide, non-magnetic iron oxide, carbon black, graphite, barium sulfate, zinc sulfide, and carbonic acid Magnesium, calcium carbonate, tungsten disulfide, molybdenum disulfide, boron nitride, silicon dioxide,
Silicon carbide, corundum, artificial diamond, garnet,
Garnet, silica, silicon nitride, molybdenum carbide, boron carbide, tungsten carbide, titanium carbide, diatomaceous earth,
Dolomite, synthetic or natural resin powder, or the like is used. Among them, carbon black, titanium oxide, barium sulfate, calcium carbonate, alumina, non-magnetic iron oxide (α-Fe ₂ O ₃ ) and the like are preferable. Incidentally, in order to improve the dispersibility, the surface treatment described above for the magnetic powder may be applied.

The size of the non-magnetic powder is preferably such that the average particle size is 0.001 to 3 μm, particularly 0.005 to 1 μm, and more preferably 0.005 to 0.5 μm. When a magnetic intermediate layer is provided, the intermediate layer contains a magnetic powder and a binder resin. Any magnetic powder may be used. For example, the powder described for the back layer and the powder described for the magnetic layer are appropriately used. Note that it is preferable to use a spinel type ferrite powder having a coercive force of 150 Oe or more. The magnetic powder preferably has an average particle diameter of 0.001 to 0.3 μm, particularly preferably 0.003 to 0.2 μm. The content is preferably 5 to 800 parts by weight, particularly preferably 10 to 700 parts by weight, based on 100 parts by weight of the binder resin of the intermediate layer.

When both the nonmagnetic powder and the magnetic powder are used, the total content thereof is determined by the binder resin 1 of the intermediate layer.
5 to 800 parts by weight, especially 10 to 70 parts by weight, per 100 parts by weight
0 parts by weight is preferred. Any one, any two or three of the magnetic layer, the back layer, and the intermediate layer contain granular, non-magnetic Mn-containing iron oxide particles.

When contained in the magnetic layer, the content thereof is 0.5 to 1 with respect to 100 parts by weight of the binder resin in the magnetic layer.
The proportion is 30 parts by weight, especially 5 to 100 parts by weight. still,
When the magnetic layer is composed of two or more layers, the granular, nonmagnetic Mn-containing iron oxide particles may be contained in all the magnetic layers. However, at least the uppermost magnetic layer (the magnetic layer farthest from the support) preferably contains the above-mentioned granular, non-magnetic Mn-containing iron oxide particles. That is, as long as it is included in the uppermost magnetic layer, it need not be included in the lower magnetic layer. When it is contained only in the uppermost magnetic layer, its content is 0.5 to 130 parts by weight, especially 5 to 100 parts by weight, based on 100 parts by weight of the binder resin in the uppermost magnetic layer. Preferably it is.
That is, the binder resin of the layer not included is not considered.

When contained in the back layer, the content is
0.1 parts by weight based on 100 parts by weight of the binder resin in the back layer
-20 parts by weight, especially 1-15 parts by weight. When it is contained in the intermediate layer, its content is 0.5 to 130 parts by weight, especially 5 to 100 parts by weight, based on 100 parts by weight of the binder resin in the intermediate layer. The coating type magnetic layer,
To form the back layer and the intermediate layer, a paint for the magnetic layer (magnetic paint), a paint for the back layer (back paint), and a paint for the intermediate layer (intermediate paint) are prepared. This is a paint in which each component is dissolved in a solvent.

Solvents used in the production of paints include ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone, and ester solvents such as methyl acetate, ethyl acetate, butyl acetate, ethyl lactate and glycol monoethyl ether. Solvents, glycol ether solvents such as ether, glycol dimethyl ether, glycol monoethyl ether and dioxane; tar (aromatic hydrocarbon) solvents such as benzene, toluene and xylene; methylene chloride, ethylene chloride, carbon tetrachloride Chlorinated hydrocarbon solvents such as chloroform, ethylene chlorohydrin and dichlorobenzene can be appropriately selected and used.

The granular, non-magnetic Mn having the above characteristics
The iron oxide-containing particles, the magnetic powder, the binder resin, the lubricant, etc. are kneaded to form a coating material. At the time of kneading, the granular, non-magnetic Mn-containing iron oxide particles having the above characteristics and the above-described components are kneaded. Are all simultaneously or individually charged into the kneader. In kneading and dispersing the paint, various kneading machines, for example, a two-roll mill, a three-roll mill, a ball mill, a pebble mill, a tron mill, a sand glider, a Szegvari attritor, a high-speed impeller disperser, a high-speed stone mill, a high-speed impact mill, a disper, A kneader, a high-speed mixer, a homogenizer, an ultrasonic disperser or the like is used.

As a method for applying the magnetic paint, the back paint, and the intermediate paint on the support, any method may be used. For example, a gravure method, a reverse method, an extrusion method and the like can be mentioned, but other methods are also possible. The magnetic layer and the intermediate layer may be formed by simultaneous multilayer coating. The coating head used for coating may be any type.

The granular, non-magnetic Mn having the above characteristics
A coating material obtained by kneading and dispersing the iron oxide particles, magnetic powder, binder and various additives in a solvent is coated on a support, oriented and cured to obtain a coating type magnetic recording medium. Curing of the coating film is performed, for example, by supplying hot air heated to 40 to 100 ° C. The degree of curing of the coating film is controlled by controlling the temperature and the supply amount.
Either the magnetic paint or the back paint may be applied first.

A magnetic recording medium can be obtained by subjecting the surface to a smoothing treatment as necessary or cutting it into a desired shape. For calendering the magnetic coating film, a super calendering method is used in which a metal roll and a cotton roll, a synthetic resin (for example, nylon, polyurethane, etc.) roll, and a metal roll and a metal roll are passed between two rolls.

Hereinafter, a specific example will be described.

[0038]

Example 1 [Components of Magnetic Coating] 100 weight of ferromagnetic metal powder (major axis length 0.08 μm, needle ratio 4.5, coercive force Hc2300 Oe, saturation magnetization 140 emu / g, BET specific surface area 50 m ² / g) Part Vinyl chloride copolymer 10 parts by weight Sulfonic acid group-containing polyurethane 5 parts by weight Granular, non-magnetic Mn-containing iron oxide (average particle size 0.2 μm, BET specific surface area 4.8 m ^{2 /} g, pH 9.5) , Water content 0.15%, tap density 1.06 g / ml, apparent density 0.48 g / ml) 10 parts by weight Carbon black (Conductex SC manufactured by Columbia Chemicals Company) 0.2 parts by weight Myristic acid 2 parts by weight Parts 100 parts by weight of methyl ethyl ketone 50 parts by weight of toluene 100 parts by weight of cyclohexanone The above composition is mixed with a sand mill for 6 hours. After dispersion, 1 part by weight of butyl stearate and 4 parts by weight of polyisocyanate (manufactured by Nippon Polyurethane Industry Co., Coronate L) and was added to obtain a magnetic paint.

[Components of Intermediate Paint] α-iron oxide (major axis length: 0.15 μm, needle ratio: 6) 100 parts by weight Vinyl chloride copolymer 10 parts by weight Sulfonate group-containing polyurethane 5 parts by weight Carbon black (Columbian Chemicals) Company Conductix SC) 2 parts by weight Alumina powder (AKP50 manufactured by Sumitomo Chemical Co., Ltd.) 5 parts by weight Myristic acid 2 parts by weight Methyl ethyl ketone 96 parts by weight Toluene 64 parts by weight Cyclohexanone 32 parts by weight The above composition is mixed and dispersed by a sand mill for 4 hours. After that, 1 part by weight of butyl stearate and 4 parts by weight of polyisocyanate (Coronate L manufactured by Nippon Polyurethane Industry Co., Ltd.) were added to obtain an intermediate paint.

[Ingredient of Back Coating] Carbon black (Raven 1255 manufactured by Columbian Chemicals Company) 100 parts by weight Alumina powder (AKP50 manufactured by Sumitomo Chemical Co., Ltd.) 10 parts by weight Vinyl chloride copolymer 15 parts by weight Sulfonic acid group-containing polyurethane 50 parts by weight Myristic acid 1 part by weight Methyl ethyl ketone 360 parts by weight Toluene 240 parts by weight Cyclohexanone 120 parts by weight After mixing and dispersing the above composition in a sand mill for 6 hours, 1 part by weight of butyl stearate and 5 parts by weight of polyisocyanate (Nippon Polyurethane) Was added to obtain a back coating.

[Magnetic Tape] The intermediate paint and the magnetic paint were applied on one surface of a PET film having a thickness of 6 μm by a simultaneous multilayer coating method. The thickness is such that the dried intermediate layer has a thickness of 1.5 μm and the magnetic layer provided on the intermediate layer has a dried thickness of 0.2 μm. Then, before the magnetic coating film has been dried, the magnetic coating film is passed through a magnetic field of 5,000 Oe to perform a magnetic field orientation treatment.
Hot air at 0 ° C. was passed through a drying furnace supplied at a rate of 15 m / sec for 30 seconds to dry.

Next, the above-mentioned back coating was applied so that the thickness after drying became 0.5 μm, and passed through a hot-air drying oven at 90 ° C. to be dried. Thereafter, calendering was performed under the conditions of a roll surface temperature of 90 ° C. and a roll linear pressure of 300 kg / cm. 8mm of raw material obtained as above
By slitting to width, a magnetic tape for 8 mm VTR was obtained.

[0043]

Example 2 The procedure of Example 1 was followed, except that the content of the granular, nonmagnetic Mn-containing iron oxide particles in the magnetic paint was 12 parts by weight.

[0044]

Example 3 The procedure of Example 1 was followed except that the content of the granular, nonmagnetic Mn-containing iron oxide particles in the magnetic paint was 15 parts by weight.

[0045]

Example 4 The granular nonmagnetic Mn-containing iron oxide particles in the magnetic paint in Example 1 had an average particle size of 0.3 μm,
BET specific surface area 10 m ^{2 /} g, pH 6.2, water content 0.
32%, tap density 1.39 g / ml, apparent density 0.3.
The method was the same as that of Example 1 except that the product of 64 g / ml was used.

[0046]

Example 5 The granular nonmagnetic Mn-containing iron oxide particles in the magnetic paint in Example 1 had an average particle size of 0.1 μm,
BET specific surface area 10 m ^{2 /} g, pH 6.3, water content 0.
33%, tap density 1.52 g / ml, apparent density 0.
The procedure was as in Example 1, except that 7 g / ml was used.

[0047]

[Comparative Example 1] In Example 1, the magnetic paint was granulated,
The procedure of Example 1 was followed except that non-magnetic Mn-containing iron oxide particles were not added.

[0048]

Comparative Example 2 In Example 1, a granular, non-magnetic Mn was used.
Α- having an average particle size of 0.2 μm instead of the iron oxide particles
The method of Example 1 was followed except that Al ₂ O ₃ was used.

[0049]

Comparative Example 3 In Example 1, a granular nonmagnetic Mn was used.
Α- having an average particle size of 0.3 μm instead of the iron oxide particles
The method of Example 1 was followed except that Al ₂ O ₃ was used.

[0050]

Example 6 [Components of Magnetic Coating] 100 weight of ferromagnetic metal powder (major axis length 0.08 μm, needle ratio 4.5, coercive force Hc2300 Oe, saturation magnetization 140 emu / g, BET specific surface area 50 m ² / g) Part Vinyl chloride copolymer 10 parts by weight Sulfonic acid group-containing polyurethane 5 parts by weight Alumina powder (AKP50 manufactured by Sumitomo Chemical Co., Ltd., average particle size 0.2 μm) 10 parts by weight carbon black (Conductex SC manufactured by Columbia Chemicals Company) 0.2 parts by weight Myristic acid 2 parts by weight Methyl ethyl ketone 100 parts by weight Toluene 50 parts by weight Cyclohexanone 100 parts by weight A magnetic paint was obtained according to the method of Example 1.

[Components of Intermediate Paint] α-iron oxide (major axis length: 0.15 μm, needle ratio: 6) 100 parts by weight Vinyl chloride-based copolymer 10 parts by weight Sulfonate group-containing polyurethane 5 parts by weight Carbon black (Columbian Chemicals) 2 parts by weight, nonmagnetic Mn-containing iron oxide (average particle size: 0.2 μm, BET specific surface area: 4.8 m ^{2 /} g, pH 9.5, water content: 0.15%, (Tap density: 1.06 g / ml, apparent density: 0.48 g / ml) 10 parts by weight Myristic acid 2 parts by weight Methyl ethyl ketone 96 parts by weight Toluene 64 parts by weight Cyclohexanone 32 parts by weight An intermediate paint is obtained according to the method of Example 1. Was.

[Components of Back Coating] Carbon black (Raven 1255 manufactured by Columbian Chemicals Company) 100 parts by weight Alumina powder (AKP50 manufactured by Sumitomo Chemical Co., Ltd.) 10 parts by weight Vinyl chloride-based copolymer 15 parts by weight Sulfonic acid group-containing polyurethane 50 parts by weight Myristic acid 1 part by weight Methyl ethyl ketone 360 parts by weight Toluene 240 parts by weight Cyclohexanone 120 parts by weight A back coating material was obtained according to the method of Example 1.

[Magnetic Tape] The intermediate paint and the magnetic paint were applied on one surface of a PET film having a thickness of 6 μm by a simultaneous multilayer coating method. The thickness is such that the dried intermediate layer has a thickness of 1.5 μm and the magnetic layer provided on the intermediate layer has a dried thickness of 0.2 μm. Then, before the magnetic coating film has been dried, the magnetic coating film is passed through a magnetic field of 5,000 Oe to perform a magnetic field orientation treatment.
Hot air at 0 ° C. was passed through a drying furnace supplied at a rate of 15 m / sec for 30 seconds to dry.

Next, the above-mentioned back coating was applied so that the thickness after drying became 0.5 μm, and passed through a hot-air drying oven at 90 ° C. to be dried. Thereafter, calendering was performed under the conditions of a roll surface temperature of 90 ° C. and a roll linear pressure of 300 kg / cm. 8mm of raw material obtained as above
By slitting to width, a magnetic tape for 8 mm VTR was obtained.

[0055]

Example 7 The procedure of Example 6 was followed, except that the content of the granular, nonmagnetic Mn-containing iron oxide in the intermediate coating composition was changed to 12 parts by weight.

[0056]

Example 8 The procedure of Example 6 was followed except that the content of the granular, nonmagnetic Mn-containing iron oxide in the intermediate coating composition was changed to 15 parts by weight.

[0057]

Example 9 The granular, nonmagnetic Mn-containing iron oxide particles in the intermediate paint in Example 6 had an average particle size of 0.3 μm.
m, BET specific surface area 10 m ² / g, pH 6.2, water content 0.32%, tap density 1.39 g / ml, apparent density 0.64 g / ml. According to.

[0058]

Example 10 The granular material in the intermediate paint in Example 6
As nonmagnetic Mn-containing iron oxide particles, an average particle size of 0.1 μm
m, BET specific surface area 10 m ² / g, pH 6.3, water content 0.33%, tap density 1.52 g / ml, apparent density 0.7 g / ml. According to.

[0059]

[Comparative Example 4] In Example 6, the intermediate paint was granular.
The procedure of Example 6 was followed except that non-magnetic Mn-containing iron oxide particles were not added.

[0060]

Comparative Example 5 In Example 6, the particles in the intermediate paint were
Instead of the non-magnetic Mn-containing iron oxide particles, the average particle size is 0.3.
The procedure of Example 6 was followed except that ₂ μm of α-Al ₂ O ₃ was used.

[0061]

Comparative Example 6 In Example 6, the particles in the intermediate paint were
Instead of the non-magnetic Mn-containing iron oxide particles, the average particle size is 0.3.
The procedure of Example 6 was followed except that 3 μm α-Al ₂ O ₃ was used.

[0062]

Example 11 [Components of Magnetic Coating] 100 weight of ferromagnetic metal powder (long axis length 0.08 μm, needle ratio 4.5, coercive force Hc2300 Oe, saturation magnetization 140 emu / g, BET specific surface area 50 m ² / g) Part Vinyl chloride copolymer 10 parts by weight Sulfonic acid group-containing polyurethane 5 parts by weight Alumina powder (AKP50 manufactured by Sumitomo Chemical Co., Ltd., average particle size 0.2 μm) 10 parts by weight carbon black (Conductex SC manufactured by Columbia Chemicals Company) 0.2 parts by weight Myristic acid 2 parts by weight Methyl ethyl ketone 100 parts by weight Toluene 50 parts by weight Cyclohexanone 100 parts by weight A magnetic paint was obtained according to the method of Example 1.

[Components of Intermediate Paint] α-iron oxide (major axis length: 0.15 μm, needle ratio: 6) 100 parts by weight Vinyl chloride-based copolymer 10 parts by weight Sulfonate group-containing polyurethane 5 parts by weight Carbon black (Columbian Chemicals) Company Conductix SC) 2 parts by weight Alumina powder (AKP50 manufactured by Sumitomo Chemical Co., Ltd.) 5 parts by weight Myristic acid 2 parts by weight Methyl ethyl ketone 96 parts by weight Toluene 64 parts by weight Cyclohexanone 32 parts by weight Intermediate paint according to the method of Example 1 I got

[Components of Back Coating] 100 parts by weight of carbon black (Raben 1255 manufactured by Columbian Chemicals Company) Granular, non-magnetic Mn-containing iron oxide (average particle size: 0.2 μm, BET specific surface area: 4.8 m ² / g, pH 6.5, water content 0.15%, tap density 1.06 g / ml, apparent density 0.48 g / ml) 10 parts by weight Vinyl chloride-based copolymer 15 parts by weight Sulfonic acid group-containing polyurethane 50 parts by weight Part 1 part by weight of myristic acid 360 parts by weight of methyl ethyl ketone 240 parts by weight of toluene 120 parts by weight of cyclohexanone A back coating material was obtained according to the method of Example 1.

[Magnetic Tape] The intermediate paint and the magnetic paint were applied on one surface of a PET film having a thickness of 6 μm by a simultaneous multilayer coating method. The thickness is such that the dried intermediate layer has a thickness of 1.5 μm and the magnetic layer provided on the intermediate layer has a dried thickness of 0.2 μm. Then, before the magnetic coating film has been dried, the magnetic coating film is passed through a magnetic field of 5,000 Oe to perform a magnetic field orientation treatment.
Hot air at 0 ° C. was passed through a drying furnace supplied at a rate of 15 m / sec for 30 seconds to dry.

Next, the above-mentioned back coating material was applied so that the thickness after drying became 0.5 μm, and passed through a hot-air drying oven at 90 ° C. to be dried. Thereafter, calendering was performed under the conditions of a roll surface temperature of 90 ° C. and a roll linear pressure of 300 kg / cm. 8mm of raw material obtained as above
By slitting to width, a magnetic tape for 8 mm VTR was obtained.

[0067]

Example 12 The procedure of Example 11 was followed except that the content of the granular, nonmagnetic Mn-containing iron oxide in the back coating was changed to 3 parts by weight.

[0068]

Example 13 The procedure of Example 11 was followed, except that the content of the granular, nonmagnetic Mn-containing iron oxide in the back coating composition was changed to 15 parts by weight.

[0069]

Example 14 The granular, nonmagnetic Mn-containing iron oxide in the back coating in Example 11 had an average particle size of 0.3 μm.
m, BET specific surface area 10 m ² / g, pH 6.2, water content 0.32%, tap density 1.39 g / ml, apparent density 0.64 g / ml. According to.

[0070]

Example 15 The granular, nonmagnetic Mn-containing iron oxide in the back coating in Example 11 had an average particle size of 0.1 μm.
m, BET specific surface area 10 m ² / g, pH 6.3, water content 0.33%, tap density 1.52 g / ml, apparent density 0.7 g / ml. According to.

[0071]

Comparative Example 7 The procedure of Example 11 was followed except that no granular, nonmagnetic Mn-containing iron oxide was added to the back coating.

[0072]

COMPARATIVE EXAMPLE 8 In Example 11, the average particle size of the non-magnetic, Mn-containing iron oxide in the back coating was changed to 0.
The procedure of Example 11 was followed except that 3 μm α-Al ₂ O ₃ was used.

[0073]

Comparative Example 9 In Example 11, the average particle size of the granular, nonmagnetic Mn-containing iron oxide in the back coating was 0.1.
The procedure of Example 11 was followed except that 1 μm of α-Al ₂ O ₃ was used.

[0074]

Example 16 [Magnetic paint] Same as the magnetic paint of Example 1. [Intermediate paint] Same as the intermediate paint of Example 6.

[Components of Back Coating] Same as back coating of Example 1. [Magnetic tape] The method of Example 1 was followed.

[0076]

Example 17 [Magnetic paint] Same as the magnetic paint of Example 1. [Intermediate paint] Same as the intermediate paint of Example 1.

[Components of back paint] Same as the back paint of Example 11. [Magnetic tape] The method of Example 1 was followed.

[0078]

Example 18 [Magnetic paint] Same as the magnetic paint of Example 6. [Intermediate paint] Same as the intermediate paint of Example 6.

[Components of back paint] Same as back paint of Example 11. [Magnetic tape] The method of Example 6 was followed.

[0080]

Example 19 [Magnetic paint] Same as the magnetic paint of Example 1. [Intermediate paint] Same as the intermediate paint of Example 6.

[Components of back paint] Same as the back paint of Example 11. [Magnetic tape] The method of Example 1 was followed.

[0082]

[Characteristics] The center line average roughness Ra, friction coefficient, scratch strength, durability, C / N, surface electric resistance, and dropout of the magnetic tape obtained in each of the above examples were examined. The results are shown in Tables 1, 2, 3, and 4 below. Ra is “Laser Interf” manufactured by Zygo.
erometric Microscope Maxim 3D Model 5700 with a 40x Fizoau lens ”and a cutoff frequency of 4.236
/ Mm, cutoff wavelength 0.236mm, Remove
d = Cylinder, Trimmed = 0, and the coefficient of friction μ was SUS304J φ
20mm tension (T ₁ ) on 4mm rod, wrap angle 115 °
And run at 14 mm / sec to measure the tension (T ₂ ), and μ = (115 / 180π) ln (T
₂ / T ₁ ), and the scratch strength is
Under a condition of 23 ° C. and 50% RH, a load of 30 g is applied to a １ ／ inch alumina sphere, and the distance of 20 mm is increased by 20 mm.
/ Slid 20 times, and examined by observing the coating film surface with a microscope of 400 times magnification.
Using a commercially available Hi8 deck, the output was reduced and tape damage was evaluated when the vehicle was repeatedly run 100 times under the conditions of 23 ° C. and 50% RH.
The i8 deck was modified to record a single wave of 9 MHz, the reproduction output (C) was observed with a spectrum analyzer, and the noise level was expressed as a noise level (N) of 8 MHz. The surface electric resistance was 8 mm. A sample of the width is measured with a digital surface electric resistance meter (R834 manufactured by ADVANTEST).
The dropout was recorded and played back using a commercially available Hi8 deck, and the dropout at that time (-10 dB or more in output was reduced for 5 μsec or more) was measured using a Shibasoku dropout counter. VH01
It was measured using BZ.

[0083] Table -1 Ra friction strength durability C / N surface electrostatic drop vapor resistance-out Example 1 2.8 0.29 ○ ○ 0.0 5 × 10 9 21 Example 2 2.9 0.29 ○ ○ -0.5 3 × 10 ⁹ 19 example 3 3.1 0.29 ○ ○ -0.7 2 × 10 9 18 example 4 2.9 0.25 ○ ○ -0.3 4 × 10 9 20 example 5 2.8 0.30 ○ ○ 0.0 5 × 10 9 23 Comparative example 1 0.40 × × 0 5 × 10 11 251 Comparative example 2 3.0 0.35 ○ △ -0.5 5 × 10 ¹¹ 222 Comparative Example 3 3.3 0.35 ○ △ -0.5 5 × 10 ¹¹ 283 * Ra is Ra on the surface of the magnetic layer, and the unit is nm.

* The coefficient of friction is the coefficient of friction of the surface of the magnetic layer. * In the strength column, ○ indicates that the coating film does not peel off at all, and X indicates that the coating film partially or completely peels off. * In the durability column, ○ indicates that the output decrease is within 5% and there is no deposit on the magnetic layer. Δ indicates that the output decrease is 5% or more or there is deposit on the magnetic layer. Is 5% or more and there is a deposit on the magnetic layer.

* C / N is based on Comparative Example 1 (0 dB). Table -2 Ra friction strength durability C / N surface electrostatic drop vapor resistance-out Example 6 2.8 0.35 ○ ○ +0.5 7 × 10 9 22 Example 7 3.0 0.35 ○ ○ 0. 0 5 × 10 ⁹ 19 example 8 3.1 0.35 ○ ○ -0.2 4 × 10 9 19 example 9 2.9 0.35 ○ ○ +0.1 5 × 10 9 23 example 10 2. 9 0.35 ○ ○ 0.0 6 × 10 9 25 Comparative example 4 3.0 0.35 × × 0 5 × 10 11 231 Comparative example 5 3.0 0.35 ○ △ -0.5 5 × 10 11 222 Comparative Example 6 3.2 0.35 ○ △ -0.5 5 × 10 ¹¹ 252 * Ra is Ra on the surface of the magnetic layer, and the unit is nm.

* The coefficient of friction is the coefficient of friction of the surface of the magnetic layer. * In the strength column, ○ indicates that the coating film does not peel off at all, and X indicates that the coating film partially or completely peels off. * In the durability column, ○ indicates that the output decrease is within 5% and there is no deposit on the magnetic layer. Δ indicates that the output decrease is 5% or more or there is deposit on the magnetic layer. Is 5% or more and there is a deposit on the magnetic layer.

* C / N is based on Comparative Example 4 (0 dB). Table 3 Ra Coefficient of friction Strength Durability Surface electric resistance Dropout Example 11 6.0 0.18 ○ 5 × 10 ⁵ 105 Example 12 6.2 0.18 ○ 5 × 10 ⁵ 118 Example 136 5.5 0.18 ○ ○ 5 × 10 ⁵ 120 Example 14 6.5 0.19 ○ ○ 5 × 10 ⁵ 121 Example 15 6.1 0.18 ○ ○ 5 × 10 ⁵ 130 Comparative Example 7 6.0 0.22 ×× 6 × 10 ⁶ 222 Comparative Example 8 6.2 0.21 ○ 8 × 10 ⁶ 231 Comparative Example 9 6.5 0.21 ○ 8 × 10 ⁶ 250 * Ra is Ra on the surface of the back layer. And the unit is nm.

* The coefficient of friction is the coefficient of friction of the back layer surface. * In the strength column, ○ indicates that the coating film does not peel off at all, and X indicates that the coating film partially or completely peels off. * In the durability column, ○ indicates that the output decrease is within 5% and there is no deposit on the magnetic layer. Δ indicates that the output decrease is 5% or more or there is deposit on the magnetic layer. Is 5% or more and there is a deposit on the magnetic layer.

* Surface electric resistance is the surface electric resistance of the back layer surface. Table -4 Ra friction strength durability C / N surface electrostatic drop vapor resistance-out Example 16 3.0 0.28 ○ ○ 0.0 7 × 10 8 14 Example 17 2.8 0.29 ○ ○ 0. 0 5 × 10 ⁹ 16 example 18 2.8 0.35 ○ ○ +0.5 7 × 10 9 15 example 19 3.0 0.28 ○ ○ 0.0 8 × 10 8 10 * Ra is the surface of the magnetic layer In Ra, the unit is nm.

* The coefficient of friction is the coefficient of friction of the surface of the magnetic layer. * The circles in the strength column and durability column are the same as in Table 1. * C / N is based on Comparative Example 1 (0 dB) As can be seen from Tables 1 and 4, granular and nonmagnetic M
By including the n-containing iron oxide particles in the magnetic layer, the surface electric resistance is reduced, and dust and dirt are less likely to adhere.
As a result, durability and running properties are improved. Then, the dropout is small, the C / N is high, and the recording / reproducing characteristics are excellent.

Further, as can be seen from Tables 2 and 4, the surface electric resistance is reduced by adding granular, non-magnetic Mn-containing iron oxide particles in the intermediate layer, and dust and dirt adhere to the intermediate layer. It becomes difficult to do. As a result, durability and running properties are improved.
Then, the dropout is small, the C / N is high, and the recording / reproducing characteristics are excellent. Table-3
As can be seen from Table 4, by including granular, non-magnetic Mn-containing iron oxide particles in the back layer, the surface electric resistance is reduced, and dust and dirt are less likely to adhere. As a result,
Durability and running performance are improved. Then, the dropout is small and the recording / reproducing characteristics are excellent.

[0092]

According to the present invention, at least one of the magnetic layer, the intermediate layer and the back layer contains granular, non-magnetic Mn-containing iron oxide particles. It becomes difficult to do. As a result, durability and running properties are improved. Then, the dropout is small and the recording / reproducing characteristics are excellent.

Claims (6)

[Claims] 1. A magnetic recording medium comprising a support and a magnetic layer provided on the support, wherein the magnetic layer contains granular, non-magnetic Mn-containing iron oxide particles. Magnetic recording medium. 2. A magnetic recording medium comprising: a support; a magnetic layer provided on one surface of the support; and a back layer provided on the other surface of the support. A magnetic recording medium comprising the Mn-containing iron oxide particles described above in the back layer. 3. A magnetic recording medium comprising: a support; a magnetic layer provided on one surface side of the support; and an intermediate layer provided between the support and the magnetic layer. A magnetic recording medium comprising nonmagnetic Mn-containing iron oxide particles in the intermediate layer. 4. The Mn-containing iron oxide particles have an average particle size of 0.1.
The magnetic recording medium according to claim 1, wherein the magnetic recording medium has a thickness of 0.5 to 0.5 μm. 5. The Mn-containing iron oxide particles have a specific surface area of 2 to 5.
The magnetic recording medium according to claim 1, wherein the magnetic recording medium has a density of 15 m ² / g. 6. The magnetic recording medium according to claim 1, wherein the Mn-containing iron oxide particles have a water content of 5% or less.