JP2745170B2 - Magnetic recording media - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording medium, a magnetic recording medium comprising a nonmagnetic support and a magnetic layer. In particular, the present invention relates to a magnetic recording medium containing a ferromagnetic metal powder in a magnetic layer.

[0002]

2. Description of the Related Art Magnetic recording media are widely used as magnetic tapes, video tapes or floppy disks. The magnetic recording medium is basically a magnetic recording medium in which a magnetic layer in which ferromagnetic powder is dispersed in a binder is laminated on a non-magnetic support.

[0003] A magnetic recording medium is required to have a high level in various characteristics such as electromagnetic conversion characteristics, running durability and running performance. In particular, with the recent spread of 8-mm video tape recorders and the like, video tapes are required to have excellent electromagnetic conversion characteristics such as excellent original image reproduction capability. In recent years, ferromagnetic metal powders exhibiting excellent magnetic properties (for example, coercive force) have been used as ferromagnetic powders in order to improve the electromagnetic conversion characteristics of magnetic recording media. The ferromagnetic metal powder is made of a ferromagnetic metal such as iron, cobalt and nickel, or an alloy powder thereof, and by using this, a magnetic recording medium having good electromagnetic conversion characteristics can be obtained.

As for ferromagnetic powder, it is generally considered that the use of finer ferromagnetic powder can improve the electromagnetic conversion characteristics of a magnetic recording medium. However, the ferromagnetic metal powder has a hardness of γ-
A magnetic recording medium manufactured according to a conventional method using a ferromagnetic metal powder because the ferromagnetic powder is lower than a ferromagnetic metal / γ-iron oxide ferromagnetic powder containing a different metal such as an iron oxide ferromagnetic powder and cobalt. The magnetic layer tends to have a lower hardness than a magnetic layer manufactured using a γ-iron oxide-based ferromagnetic powder or a dissimilar metal / γ-iron oxide-based ferromagnetic powder. Therefore, the magnetic layer of the magnetic recording medium using the ferromagnetic metal powder is easily damaged by contact with a magnetic head or the like during running. In the magnetic layer damaged in this way, its electromagnetic conversion characteristics are deteriorated, so that the purpose using the ferromagnetic metal powder cannot be achieved.

Therefore, usually, when a ferromagnetic metal powder is used, a large amount of an abrasive is added to the magnetic layer to form a portion having high hardness in the magnetic layer, and the magnetic layer and a traveling system such as a magnetic head are used. A method of preventing damage to the magnetic layer due to contact with a member is employed. That is, if the content of the abrasive becomes high,
Utilizing the fact that the portion of the magnetic layer having high hardness increases, so that the magnetic layer is hardly damaged.

However, in practice, if a magnetic layer using a ferromagnetic metal powder is mixed with a large amount of an abrasive so as to exhibit good strength, it is necessary to reduce the content of the ferromagnetic metal powder. Come. Therefore, there is a problem that the obtained magnetic recording medium does not easily exhibit sufficient electromagnetic conversion characteristics despite the use of the ferromagnetic metal powder.

[0007] As described above, the main factors for improving the electromagnetic conversion characteristics are:
Since it is a ferromagnetic metal powder, the abrasive does not directly contribute to the improvement of the electromagnetic conversion characteristics. Therefore, in a magnetic recording medium which is required to exhibit particularly high electromagnetic conversion characteristics, such as an 8 mm video tape, the electromagnetic conversion characteristics associated with a decrease in the compounding ratio of the ferromagnetic metal powder due to the addition of a large amount of an abrasive. Is particularly problematic.

On the other hand, it is known that a small amount of aluminum is added during the production of a ferromagnetic metal powder for the purpose of preventing sintering of particles during heat reduction (for example, Japanese Patent Publication No. Sho 59-59).
No. -19163), however, it is not known at all how the obtained ferromagnetic metal powder functions in the magnetic layer. Therefore, while showing good running durability,
With the aim of providing a magnetic recording medium in which the properties of ferromagnetic metal powders having excellent magnetic properties were sufficiently exhibited,
In a magnetic recording medium comprising a non-magnetic support and a magnetic layer in which a ferromagnetic metal fine powder and an abrasive are dispersed in a binder provided on the support, the ferromagnetic metal fine powder is converted into metal. Comprising from 1 to 6% by weight of an aluminum component,
A magnetic recording medium has been proposed in which the abrasive of the magnetic layer is mainly composed of one selected from α-alumina, chromium oxide, silicon carbide and silicon nitride (JP-A-63-103424). No. gazette.).

Although this proposal has demonstrated excellent effects such as abrasion resistance, output reduction, and C / N ratio with an 8 mm video tape, if such a technique is applied to a video tape for broadcasting as it is. , Durability, output, and storage stability could not be satisfied. As a result of analyzing the factors affecting the durability, output, and storage stability, the amount of the alumina as the sintering inhibitor of the ferromagnetic metal powder, the thickness of the oxide film of the ferromagnetic metal powder, the amount of the abrasive, and the rust prevention were investigated. It was found that the presence or absence of the agent greatly affected the present invention.

[0010]

SUMMARY OF THE INVENTION An object of the present invention is to provide a magnetic recording medium having excellent storage stability, high output and C / N characteristics, and excellent durability.

[0011]

SUMMARY OF THE INVENTION An object of the present invention is to provide a magnetic recording medium having a magnetic layer containing a ferromagnetic metal powder, a binder and an abrasive on a non-magnetic support. Aluminum, the content of which is 2 to 5% by weight based on the ferromagnetic metal powder, the crystal size of an oxide film of the ferromagnetic metal powder is 15 to 50 °, and the magnetic layer is 10 for 100 parts by weight of powder
It comprises 20 parts by weight of the abrasive, and the magnetic layer is below one
Selected from the compounds represented by the general formulas (1) to (4)
This can be achieved by a magnetic recording medium characterized by containing at least one organic phosphorus compound . (1) (R-O) n PO (OM) 3-n (2) (R-O) n P (OM) 3-n (3) (R) n P (OM) 3-n (4) RPO (OM) ₂ (In each formula, R represents a substituted or unsubstituted alkyl having 6 to 40 carbon atoms.
Kill group, aralkyl group, alkylphenyl group, alkyl
A phenylalkylene oxide group, an alkenyl group, or
M represents a hydrogen atom, an alkali metal or-
N (R ¹ ) ₄ , wherein R ¹ is an alkyl having 1 to 20 carbon atoms
And n represents 1 or 2. )

The magnetic recording medium of the present invention is achieved by defining the following four factors. Al is contained on the surface of the ferromagnetic metal powder so that the amount of Al is 2 to 5% by weight. The crystallite size of the oxide film of the ferromagnetic metal powder is 15 to 5
Control to 0 °. The magnetic layer contains at least a specific organic phosphorus compound . Abrasive is added to 10 parts by weight of ferromagnetic metal powder.
Contains 20 parts by weight.

That is, by adding Al than the ferromagnetic metal powder alone, the hardness increases, and if the durability is the same without using the factor, the amount of the abrasive is reduced, and the ferromagnetic metal powder is reduced. And the output can be improved. Also, if the same filling degree as the ferromagnetic metal powder of the magnetic recording medium created without using the same factor is sufficient,
Since the amount of the abrasive added can be increased, the durability can be improved.

Further, the output can be improved by reducing the thickness of the oxide film as described above. The decrease in storage stability due to the reduction in the thickness of the oxide film can achieve both output and storage stability by using at least one or more organic phosphorus compounds . Further, in order to improve the durability, the amount of the abrasive is increased as described above, and the decrease in the degree of filling caused by the increase in the amount of the abrasive is covered by the above-described output improvement.

In other words, the and factors have a positive effect on the output and the degree of filling of the ferromagnetic metal powder, but have a negative effect on the preservability and durability, and By defining this, it was possible to correct this negative effect, to compensate for and improve mutually contradictory characteristics. In the present invention, the amount of Al on the surface of the ferromagnetic metal powder is 2 to that of the ferromagnetic powder.
Means for making the content to be 5% by weight is arbitrary. Here, the weight percent of Al means the weight percent of Al in terms of metal. That is, the existence form and composition of Al on the surface of the ferromagnetic metal powder are arbitrary, but it is sufficient that Al can be at least a factor for forming an oxide film on the surface. Generally, the Al
Is present in the oxide film as an oxide composition, but the composition is also arbitrary. The oxide film can include an element other than Al.

The abundance of Al in the oxide film is 1 atomic% or more, preferably 5 atomic% or more in terms of metal. In the present invention, the crystallite size of the oxide film of the ferromagnetic metal powder is controlled to. 15 to 50 Å, more preferably <br/> rather is controlled to 20～40A. As a means for forming the oxide film, a conventionally known method can be appropriately applied. For example, a compound containing at least Al as a metal component in a metal oxide of a ferromagnetic metal powder raw material, for example, iron oxyhydroxide, cobalt hydroxide, α-Fe ₂ O ₃ or the like (for example, sulfuric acid called a sintering inhibitor) (A salt, a nitrate, etc.), which is reduced, and then oxidized to form an oxide film containing at least Al on the metal surface.

The reduction conditions in this case include a method of treating in a dry hydrogen gas atmosphere at 300 to 600 ° C. for 30 minutes to 24 hours. In addition, the oxidation treatment conditions may be oxidation in a gas phase or oxidation in a liquid phase, and the oxidation conditions can be variously selected, and by appropriately adjusting the oxygen partial pressure, the temperature, and the like, the above-described regulation of the oxide film is performed. The range can be controlled, and any oxidation treatment other than the normal slow oxidation treatment can be performed.

The conditions of the slow oxidation treatment include, for example, oxidation of dried and dehydrated air and dry nitrogen in a container from a ratio of 1:20 to 1: 0 at 25 to 60 ° C. over 2 to 24 hours. Can be In addition, the liquid phase oxidation treatment conditions include:
The method includes blowing air in an organic solvent to perform slow oxidation, and in this case, heating the solvent when evaporating the solvent, and the like.

If desired, after the gas phase oxidation, a heat treatment in an oxygen-containing gas at a temperature of 25 to 60 ° C. or higher for a desired time, usually 30 minutes or longer, can also be carried out. Further, ozone oxidation, plasma oxidation, or the like can also be used. Examples of metal elements other than Al that can form the oxide film include Si, Ti, and B.
These are used in the form of a salt or a compound in the same manner as Al, and the adhesion to the metal oxide is carried out, for example, by mixing the metal oxide in a suspension thereof, washing with water, drying, and heating and dehydrating. Is mentioned.

[0020] Examples of the organic phosphorus compound is a factor, it is preferable to have a function, such as improving dispersibility in addition to the main serving anticorrosive function. The organic phosphorus compound is its existing form if it is present in the magnetic layer is optional, preferably it is desirable to use a material obtained by coating the surface of the ferromagnetic metal powder in an organic phosphorus compound.

As a coating method, a ferromagnetic metal powder is suspended in an organic solvent, and an organic phosphor
After adding the compound , a method of drying is used. Coated
The amount of the organic phosphorus compound is 0.1 to 100 parts by weight, preferably 0.5 to 5 parts by weight, based on 100 parts by weight of the ferromagnetic metal powder .

In the present invention, the following organic phosphorus compounds having a function of preventing rust and a function of increasing the dispersibility of the ferromagnetic metal powder are used . (1) (RO) _n PO (OM) _3-n (2) (RO) _n P (OM) _3-n (3) (R) _n P (OM) _3-n (4) RPO (OM) _{2 In} each formula, R represents a substituted or unsubstituted alkyl group having 6 to 40 carbon atoms, an aralkyl group, an alkylphenyl group, an alkylphenylalkylene oxide group, an alkenyl group, or an aryl group, and M represents a hydrogen atom. , Alkali metal or -N
(R ¹ ) ₄ , R ¹ represents an alkyl group having 1 to 20 carbon atoms, and n represents 1 or 2.

In the present invention, the combination of the phenylphosphonic acid represented by (4) and the phosphate ester represented by (1) is most suitable, and the mixing ratio of phenylphosphonic acid to phosphate ester is 1 to 5 by weight. The range is 10:10 to 1, preferably 1 to 5: 5 to 1. The amount of the organophosphorus compound used is 0.1 to 100 parts by weight of the ferromagnetic metal powder.
It is selected from the range of 1 to 10 parts by weight, preferably 0.5 to 7 parts by weight.

In the present invention, the above-mentioned abrasive is contained in the magnetic layer in an amount of 10 to 20% by weight, preferably 10 to 15% by weight, based on the ferromagnetic metal powder. It is preferable to use a material having a composition including the same. That is, when the material is used as the polishing agent, a special effect can be expected in improving the durability. However, although the details of the mechanism are unknown, the polishing agent and the surface of the ferromagnetic metal powder can be expected. It is considered that the affinity with existing Al atoms is enhanced, and as a result, large durability can be achieved with a small amount.

The polishing agent preferably has a Mohs hardness of 9 or more, and specifically, α-Al ₂ O ₃ is particularly preferable. Hereinafter, other items that can be appropriately selected will be described mainly with respect to the above-described factors of the present invention. The ferromagnetic metal powder used in the present invention is not particularly limited as a base material, and may be an alloy or a simple metal, particularly one containing iron, cobalt or nickel. Its specific surface area (S _BET )
Is 40 m ² / g or more, preferably 50 m ² / g or more, and the coercive force is 1000 to 3000 Oe, more preferably 1550 Oe or more. Bm is 250
0 gauss or more, preferably 2800 gauss or more, and the saturation magnetization (? _S ) is preferably 100 to 200.

The crystallite size of the metal component portion of the ferromagnetic metal powder excluding the oxide film is preferably in the range of 100 to 220 °, preferably 140 to 200 °. If it is less than 100 °, it is not preferable because of poor dispersibility, and 220 °
If it is larger, C / N is not preferable because of poor quality. The shape of the ferromagnetic metal powder is not particularly limited, but usually a needle-like, granular, dice-like, rice-granular or plate-like material is used.

As an example of the ferromagnetic metal powder, the metal content in the ferromagnetic metal powder is 60% by weight or more, and 70% by weight or more of the metal content is at least one type of ferromagnetic metal or alloy (eg, Fe, Co, Ni, Fe-Co, F
e-Ni, Co-Ni, Co-Ni-Fe), and other components (eg, Al, Si, S, Sc) within a range of 40% by weight or less, more preferably 20% by weight or less. , T
i, V, Cr, Mn, Cu, Zn, Y, Mo, Rh, P
d, Ag, Sn, Sb, Te, Ba, Ta, W, Re,
Au, Hg, Pb, Bi, La, Ce, Pr, Nd,
B, P), and alloys, iron nitride, and iron carbide that may contain P). The ferromagnetic metal powder contains a small amount of water, hydroxide or oxide, an alkali metal element (Na,
K) and those containing alkaline earth metal elements (Mg, Ca, Sr).

The following are typical methods for producing these ferromagnetic metal powders. (A) A method of reducing a complex organic acid salt (mainly oxalate) with a reducing gas such as hydrogen (b) A method of reducing iron oxide with a reducing gas such as hydrogen to obtain Fe or Fe—Co particles or the like (C) a method of thermally decomposing a metal carbonyl compound; (d) sodium borohydride in an aqueous solution of a ferromagnetic metal;
Method of reducing by adding a reducing agent such as hypophosphite or hydrazine (e) Method of electrolytically depositing ferromagnetic metal powder using a mercury cathode and then separating it from mercury (f) Low-pressure inertness of metal Method of Evaporating in Gas to Obtain Fine Powder The above method can be appropriately applied to form the ferromagnetic metal powder having an oxide film of the present invention, but the method (b) is preferable as described above. Further, in the present invention, one ordinary ferromagnetic metal powder which is not the ferromagnetic metal powder of the present invention is used.
It can be used in the range of 0% by weight or less.

The abrasive for the magnetic layer or the back layer used in the present invention is used for improving the durability of the magnetic tape and the head cleaning effect of the VTR, and is generally a material having an abrasive action or a polishing action. -Alumina, γ
-Alumina, α-γ-alumina, fused alumina, silicon carbide, chromium oxide, cerium oxide, corundum, artificial diamond, α-iron oxide, garnet, emery (main component:
Corundum and magnetite), garnet, silica, silicon nitride,
Materials such as boron nitride, molybdenum carbide, boron carbide, tungsten carbide, titanium carbide, tripoly, diatomaceous earth, dolomite, etc., which are mainly used in combination of up to four kinds of Mohs hardness of 6 or more. Those having an average particle size of 0.005 to 5 μm are used,
Particularly preferably, it is 0.01 to 2 μm. In the case of the back layer, it is desirable to use 0.01 to 5 parts by weight based on 100 parts by weight of the resin.

The powdery lubricant used in the magnetic layer or the back layer according to the present invention includes graphite, molybdenum disulfide, boric acid, graphite fluoride, calcium carbonate, barium sulfate, silicon oxide, titanium oxide, zinc oxide, and the like. Inorganic fine powders such as tin oxide and tungsten disulfide, acrylic styrene resin fine powder, benzoguanamine resin fine powder, melamine resin fine powder, polyolefin resin fine powder, polyester resin fine powder, polyamide resin fine powder, polyimide And fine resin powders such as fine resin powder and polyfluoroethylene resin fine powder.

As the organic compound-based lubricant, silicone oil (dialkyl polysiloxane, dialkoxy polysiloxane, phenyl polysiloxane, fluoroalkyl polysiloxane (KF96, KF69 manufactured by Shin-Etsu Chemical Co., Ltd.)
Etc.), fatty acid-modified silicone oil, fluorinated alcohol,
Polyolefin (polyethylene wax, polypropylene, etc.), polyglycol (ethylene glycol, polyethylene oxide wax, etc.), tetrafluoroethylene oxide wax, polytetrafluoroglycol, perfluoroalkyl ether, perfluorofatty acid, perfluorofatty acid ester, perfluoroalkyl sulfate , Perfluoroalkylsulfonic acid ester,
Compounds into which fluorine or silicon is introduced, such as perfluoroalkylbenzenesulfonic acid esters and perfluoroalkylphosphate esters; alkyl sulfates, alkyl sulfonates, alkyl phosphonate triesters, alkyl phosphonate monoesters, alkyl phosphonate diesters, alkyl phosphates Organic acids and organic acid ester compounds such as esters and succinates; heterocyclic compounds containing nitrogen and sulfur such as triazaindolizine, tetraazaindene, benzotriazole, benzotriazine, benzodiazole and EDTA; carbon Any one or two or more of monobasic fatty acids having a number of 10 to 40 and monohydric alcohol or dihydric alcohol having 2 to 40 carbon atoms, trihydric alcohol, tetrahydric alcohol, and hexahydric alcohol Consisting of Fatty acid esters, fatty acid esters comprising monobasic fatty acids having 10 or more carbon atoms and monohydric to hexahydric alcohols having a total of 11 to 70 carbon atoms when added to the carbon atoms of the fatty acids, and having 8 carbon atoms Up to 40 fatty acids, fatty acid amides, fatty acid alkyl amides, and aliphatic alcohols can also be used.

Specific examples of these compounds include butyl caprylate, octyl caprylate, ethyl laurate, butyl laurate, octyl laurate, ethyl myristate, butyl myristate, octyl myristate, 2-ethylhexyl myristate, Ethyl palmitate, butyl palmitate, octyl palmitate, 2 ethylhexyl palmitate, ethyl stearate, butyl stearate, isobutyl stearate, octyl stearate, 2 ethylhexyl stearate, amyl stearate, isoamyl stearate, 2 stearic acid
Ethylpentyl, 2-hexyldecyl stearate, isotridecyl stearate, stearic acid amide, alkyl stearic acid, butoxyethyl atearate,
Anhydrosorbitan monostearate, anhydrosorbitan distearate, anhydrosorbitan tristearate, anhydrosorbitan tetrastearate, oleyl oleate, oleyl alcohol, lauryl alcohol, montan wax, carnauba wax, etc. alone or in combination Can be used.

As the lubricant used in the present invention, so-called lubricating oil additives can be used alone or in combination, and oily agents (rapeseed oil, lauryl alcohol, etc.), extreme pressure agents (dibenzyl sulfide, tricresyl) Phosphate, tributyl phosphite, etc.), detergents / dispersants, viscosity index improvers, pour point depressants, foaming agents and the like. These lubricants are added in the range of 0.01 to 30 parts by weight based on 100 parts by weight of the binder.

The dispersing agents and dispersing agents used in the present invention include caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, elaidic acid, linoleic acid, linolenic acid, and stearolic acid. Fatty acids having 2 to 40 carbon atoms (R ₁ COOH, R ₁ is an alkyl group having ₁ to 39 carbon atoms, phenyl group, aralkyl group) such as behenic acid, maleic acid and phthalic acid; alkali metals of the above fatty acids (Li, Na, K) or NH ₄ ^+, etc. or alkaline earth metals (Mg, Ca, Ba, etc.), Cu, P
b) metal soap (copper oleate), fatty acid amide; lecithin (soybean oil lecithin) and the like are used. In addition, higher alcohols having 4 to 40 carbon atoms (butanol, octyl alcohol, myristyl alcohol, stearyl alcohol) and their sulfates and amine compounds can also be used. Also, polyethylene glycol,
Polyethylene oxide, sulfosuccinic acid, metal sulfosuccinate, sulfosuccinate, the above-mentioned organic phosphorus compound, and the like can also be included. When these dispersants are used in the magnetic layer, the amount is from 0.005 to 20 parts by weight, preferably from 0.1 to 5 parts by weight, based on 100 parts by weight of the binder. Also,
When used for the back layer, 0.005 to 20 parts by weight, preferably 0.01 to 5 parts by weight, per 100 parts by weight of the binder.
It is in the range of parts by weight.

As to the method of using these dispersants, as described above, not only the ferromagnetic powder but also the surface of the nonmagnetic powder may be applied in advance, or they may be added during dispersion. Such materials are disclosed, for example, in JP-B-39-28369, JP-B-44-17945, JP-B-44-18221, JP-B-48-7441, JP-B-48-15001, JP-B-48-15002, and JP-B-48-15002. JP-B-48-16363, JP-B-49-39402, U.S. Pat.
No. 3470021, and the like.

As the antifungal agent used in the present invention, 2-
(4-thiazolyl) -benzimidazole, N- (fluorodichloromethylthio) -phthalimide, 10,1
0'-oxybisphenoxalcin, 2,4,5,6-
Examples include tetrachloroisophthalonitrile, p-tolyldiiodomethylsulfone, triiodoallyl alcohol, dihydroacetoic acid, mercury phenyloleate, bis (tributyltin) oxide, and salicylanilide. Such a substance is described in, for example, "Microbial Disaster and Prevention Technology", Engineering Book of 1972, "Chemistry and Industry", 32, 904 (1979).

The carbon black used in the magnetic layer and the back layer of the present invention may be a furnace for rubber, a thermal for rubber,
Color black, acetylene black and the like can be used. These carbon blacks are used for the purpose of improving the durability of the tape, such as an antistatic agent, a light shielding agent, a friction coefficient adjusting agent, and the like. Specific examples of abbreviations in the United States of these carbon blacks include SAF, ISAF, and IISA.
F, T, HAF, SPF, FF, FEF, HMF, GP
F, APF, SRF, MPF, ECF, SCF, CF,
FT, MT, HCC, HCF, MCF, LFF, RCF
And the like, and the US ASTM standard D-1765-82a
Can be used. The average particle size of these carbon blacks used in the present invention is 5 to 1000 mμ (electron microscope), the specific surface area by the nitrogen adsorption method is 1 to 800 m ² / g, and the pH is 4 to 11 (JIS K-6221-1982 method). ), Dibutyl phthalate (DBP) oil absorption is 10-800 ml / 100 g (JI
S standard K-6221-1982 method). The size of the carbon black used in the present invention is 5 to 100 mμ of carbon black for the purpose of lowering the surface electric resistance of the coating film, and 50 to 10 when controlling the strength of the coating film.
Use 00 mμ of carbon black. In order to control the surface roughness of the coating film, fine carbon black (100%) is used for smoothing to reduce spacing loss.
coarse particles (less than 100 μm) are used for the purpose of reducing the friction coefficient by roughening the surface. As described above, the type and the amount of carbon black to be used are properly used depending on the purpose required for the magnetic recording medium. Further, these carbon blacks may be subjected to a surface treatment with a dispersant described below or the like, or may be used after being grafted with a resin. In addition, the furnace temperature for producing carbon black was set to 2000 ° C.
What processed the above and a part of surface was graphitized can also be used. Also, hollow carbon black can be used as a special carbon black.

In the case of a magnetic layer, these carbon blacks are preferably used in an amount of 0.1 to 30 parts by weight based on 100 parts by weight of the ferromagnetic powder. In the case of the back layer, it is desirable to use 20 to 400 parts by weight based on 100 parts by weight of a resin described later. The carbon black that can be used in the present invention can be referred to, for example, "Carbon Black Handbook" edited by Carbon Black Association (published in 1971). Examples of these carbon blacks are described in US Pat.
39257, U.S. Pat.
-92424 and JP-A-61-99927.

As the antistatic agent other than carbon black used in the present invention, graphite, denatured graphite,
Conductive powders such as carbon black graft polymer, tin oxide-antimony oxide, tin oxide, titanium oxide-tin oxide-antimony oxide; natural surfactants such as saponin; alkylene oxide-based, glycerin-based, glycidol-based, and polyhydric alcohol Nonionic surfactants such as polyhydric alcohol esters and alkylphenol EO adducts; higher alkylamines, cyclic amines, hydantoin derivatives,
Cationic surfactants such as amidoamines, esteramides, quaternary ammonium salts, pyridine and other heterocycles, phosphoniums or sulfoniums; carboxylic acids, sulfonic acids, phosphonic acids, phosphoric acids, sulfates, sulfates, phosphonates, phosphates Anionic surfactants containing acidic groups such as; amino acids; aminosulfonic acids;
Sulfuric acid or phosphoric acid esters of amino alcohol, amphoteric surfactants such as alkyl betaine type and the like are used. These surfactants may be added alone or as a mixture.
The amount of these surfactants used in the magnetic recording medium is 0.01 to 10 per 100 parts by weight of the ferromagnetic metal powder.
Parts by weight. The amount used in the back layer is the amount of the binder 1
It is 0.01 to 30 parts by weight per 00 parts by weight. These are used as antistatic agents, but are sometimes applied for other purposes, such as dispersion, improvement of magnetic properties, improvement of lubricity, coating aids, curing accelerators, and dispersion accelerators. .

As the binder used in the magnetic layer of the present invention or the back layer provided as desired, conventionally known thermoplastic resins, thermosetting resins, reactive resins, electron beam-curable resins, ultraviolet-curable resins, visible light Light curable resins and mixtures thereof are used. The thermoplastic resin has a softening temperature of 150 ° C. or less and an average molecular weight of 10,000 to 300.
000, having a degree of polymerization of about 50 to 2000, more preferably about 200 to 600. For example, vinyl chloride vinyl acetate copolymer, vinyl chloride copolymer, vinyl chloride vinyl acetate vinyl alcohol copolymer, chloride Vinyl vinyl alcohol copolymer, vinyl chloride vinylidene copolymer, vinyl chloride acrylonitrile copolymer, acrylate acrylonitrile copolymer, acrylate vinylidene chloride copolymer, acrylate styrene copolymer, methacrylic ester Acrylonitrile copolymer, methacrylic acid ester vinylidene chloride copolymer, methacrylic acid ester styrene copolymer, urethane elastomer, nylon-silicone resin, nitrocellulose-polyamide resin, polyfukka vinyl, vinylidene chloride acryloyl Tolyl copolymer, butadiene acrylonitrile copolymer, polyamide resin, polyvinyl butyral, cellulose derivative (cellulose acetate butyrate, cellulose diacetate, cellulose triacetate, cellulose propionate, nitrocellulose, ethyl cellulose, methyl cellulose, propyl cellulose, methyl ethyl cellulose, Carboxymethylcellulose, acetylcellulose, etc.), styrene-butadiene copolymer, polyester resin, polycarbonate resin, chlorovinyl ether acrylate copolymer, amino resin, various synthetic rubber-based thermoplastic resins, and mixtures thereof. .

The thermosetting resin or the reactive resin has a molecular weight of 200,000 or less in the state of a coating solution.
By heating and humidifying after drying, the molecular weight becomes infinite due to reactions such as condensation and addition. Among these resins, those which do not soften or melt before the resin is thermally decomposed are preferred. Specifically, for example, a phenol resin, a phenoxy resin, an epoxy resin, a polyurethane resin, a polyester resin, a polyurethane polycarbonate resin, a urea resin, a melamine resin, an alkyd resin, a silicone resin, an acrylic reaction resin (an electron beam curing resin), and an epoxy-polyamide Resin, nitrocellulose melamine resin, mixture of high molecular weight polyester resin and isocyanate prepolymer, mixture of methacrylate copolymer and diisocyanate prepolymer, mixture of polyester polyol and polyisocyanate, urea formaldehyde resin, low molecular weight glycol / high molecular weight A diol / triphenylmethane triisocyanate mixture, a polyamine resin, a polyimine resin, and mixtures thereof.

These thermoplastic resins, thermosetting resins, and reactive resins have carboxylic acid (COOM), sulfinic acid, sulfenic acid, sulfonic acid (SO ₃ M), phosphoric acid (OPO) as functional groups other than the main functional groups. Acidic groups (M is H, alkali metal, alkaline earth metal, hydrocarbon group) such as (OM) ₂ ), phosphonic acid (PO (OM) ₂ ), sulfuric acid (OSO ₃ M) and ester groups thereof; Amino acids; aminosulfonic acids, sulfuric acid or phosphoric acid esters of amino alcohols, amphoteric groups such as alkyl betaine, amino groups, imino groups, imide groups, amide groups, etc .;
Alkoxyl, thiol, alkylthio, halogen (F, Cl, Br, I), silyl, siloxane, epoxy, isocyanato, cyano, nitrile, oxo, acryl, phosphine Or more and up to 6 types, and each functional group is 1 × 1
It is preferable to contain 0 ^-6 eq to 1 × 10 ^-2 eq.

These binders may be used alone or in combination, and other additives may be added. The mixing ratio of the ferromagnetic metal powder and the binder in the magnetic layer is in the range of 5 to 300 parts by weight, preferably 10 to 100 parts by weight of the binder with respect to 100 parts by weight of the ferromagnetic metal powder. The mixing ratio of the fine powder of the back layer and the binder is 10
The binder is used in an amount of 8 to 400 parts by weight, preferably 20 to 150 parts by weight, based on 0 parts by weight. Examples of the additives include the above-mentioned dispersants, lubricants, abrasives, antistatic agents, antioxidants, solvents and the like.

The polyisocyanate used in the magnetic layer and / or the back layer of the present invention includes tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, naphthylene-1,5-diisocyanate, o- Isocyanates such as toluidine diisocyanate, isophorone diisocyanate, triphenylmethane triisocyanate, isophorone diisocyanate, products of the isocyanates and polyalcohols, and 2-1 formed by condensation of isocyanates.
A zero-mer polyisocyanate or a product of a polyisocyanate and a polyurethane having a terminal functional group of isocyanate can be used. The average molecular weight of these polyisocyanates is preferably from 100 to 20,000. Commercially available trade names of these polyisocyanates include Coronate L, Coronate H
L, Coronate 2030, Coronate 2031, Millionate MR, Millionate MTL (manufactured by Nippon Polyurethane Co., Ltd.), Takenate D-102, Takenate D-1
10N, Takenate D-200, Takenate D-20
2, Takenate 300S, Takenate 500 (manufactured by Takeda Pharmaceutical Co., Ltd.), Sumidur T-80, Sumidur 44
S, Sumidule PF, Sumidule L, Sumidule N, Death module L, Death module IL, Death module N, Death module HL, Death module T6
5, death module 15, death module R, death module RF, death module SL, death module Z4
273 (manufactured by Sumitomo Bayer), and these can be used alone or in combination of two or more using the difference in curing reactivity. For the purpose of accelerating the curing reaction, a compound having a hydroxyl group (butanediol, hexanediol, polyurethane having a molecular weight of 1,000 to 10,000, water, etc.), an amino group (monomethylamine, dimethylamine, trimethylamine, etc.) or a metal oxide A catalyst or a catalyst such as iron acetyl acetate can be used in combination. It is desirable that these compounds having a hydroxyl group or an amino group are polyfunctional. The polyisocyanate is preferably used in the magnetic layer and the back layer in an amount of 2 to 70 parts by weight, more preferably 5 to 50 parts by weight, per 100 parts by weight of the total amount of the binder resin and the polyisocyanate. These examples are described in JP-A-60-131622.
And JP-A-61-74138.

In the present invention, the organic solvent used for dispersion, kneading, and application for preparing the magnetic coating material and the back layer coating material may be acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, or the like in any ratio. Ketones such as isophorone and tetrahydrofuran; methanol, ethanol, propanol, butanol, isobutyl alcohol, isopropyl alcohol,
Alcohols such as methylcyclohexanol; esters such as methyl acetate, ethyl acetate, butyl acetate, isobutyl acetate, isopropyl acetate, ethyl lactate, and glycol monoethyl ether; diethyl ether, tetrahydrofuran, glycol dimethyl ether, glycol monoethyl ether, dioxane Ethers such as benzene; toluene, xylene, cresol, chlorobenzene, and tar (aromatic hydrocarbons) such as styrene; methylene chloride, ethylene chloride, carbon tetrachloride,
Chlorinated hydrocarbons such as chloroform, ethylene chlorohydrin and dichlorobenzene, N, N-dimethylformaldehyde, hexane and the like can be used. These solvents are usually used in two or more kinds in an arbitrary ratio. In addition, trace amounts of impurities (polymers of the solvent itself,
Moisture, raw material components, etc.).

These solvents may be used as a magnetic coating material or a backing layer coating material, or a total solid content of an undercoating liquid for an undercoating layer described below, of 10%.
It is used in an amount of 100 to 20,000 parts by weight based on 0 parts by weight. The preferred solid content ratio of the magnetic paint is 10 to 40% by weight.
It is. Further, the preferred solid content ratio of the back layer paint is,
5 to 20% by weight. In addition, an aqueous solvent (water, alcohol, acetone, etc.) can be used instead of the organic solvent.

The magnetic layer is formed by coating, drying and orienting on a support as a magnetic coating solution prepared by arbitrarily combining the above compositions and the like. When used as a tape, the support preferably has a thickness of about 2.5 to 100 microns, preferably about 4 to 10 microns. In the case of a disk or card, the thickness is about 0.03 to 10 mm, and in the case of a drum, it can be used in a cylindrical shape. Materials include polyesters such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), polyolefins such as polypropylene, cellulose derivatives such as cellulose triacetate and cellulose diacetate, vinyl resins such as polyvinyl chloride, polycarbonate, and polyimide. In addition to plastics such as polyamide and polysulfone, metals such as aluminum and copper, and ceramics such as glass can also be used. Among these materials, PET, PE
N and aramid are particularly preferred. Prior to coating, these supports are subjected to corona discharge treatment, plasma treatment, undercoat treatment,
Heat treatment, dust removal treatment, metal deposition treatment, and alkali treatment may be performed. Regarding these supports, for example, West German Patent 3,338,854A, JP-A-59-116926, JP-A-61-129731, U.S. Pat. No. 4,388,368.
No .: Yukio Mitsuishi, Textile and Industry, vol. 31, p. 50-55,
It is described in 1975 and the like. In the case of a video tape or the like, the Young's modulus (F5 value) of these supports can be selected from ² to 30 kg / mm ² in both the width direction and the longitudinal direction depending on the purpose. It is preferable that at least one surface of the support has a surface roughness (Ra) of 15 nm or less.

The method of dispersion and kneading is not particularly limited, and the order of addition of each component (resin, powder, lubricant, solvent, etc.)
The addition position during dispersion / kneading, the dispersion temperature (0 to 80 ° C.) and the like can be appropriately set. For preparing the magnetic paint and the back layer paint, a usual kneading machine, for example, a two-roll mill, a three-roll mill, a ball mill, a pebble mill, a tron mill, a sand grinder, a Segvar (Szegvar) is used.
i), attritor, high-speed impeller, disperser, high-speed stone mill, high-speed impact mill, disper, kneader,
High-speed mixers, ribbon blenders, co-kneaders, intensive mixers, tumblers, blenders, dispersers, homogenizers, single-screw extruders, twin-screw extruders, and ultrasonic dispersers can be used. Usually, these kneading and dispersion
Equipped with a plurality of kneaders, and continuously process. For details of the kneading and dispersing technique, see C. PATON (T.C. Patton) “Paint Flow and Pigment Dispersio
n "(Paint Flow and Pigment Dispersion) published in 1964 by John Wiley & Sons (John Wiley and Sons), Shinichi Tanaka," Industrial Materials ", Vol. 25, 37 (1977), and references cited in the book. I have. As an auxiliary material for these dispersion and kneading, in order to promote the dispersion and kneading efficiently, 10c
Steel balls, steel beads, ceramic beads, glass beads, and organic polymer beads having a diameter of mφ to 0.05 mmφ can be used. These materials are not limited to spherical shapes. Further, it is described in the specification of U.S. Patent Nos. 2,581,414 and 2,855,156. Also in the present invention, the magnetic paint and the back layer paint can be prepared by kneading and dispersing according to the method described in the above-mentioned book and the literature cited therein.

As a method of applying the above-mentioned magnetic coating material and back layer coating material on a support, the viscosity of the coating solution is preferably 1 to 2
000 centistokes (25 ° C), air doctor coat, blade coat, air knife coat,
Squeeze coat, impregnation coat, reverse roll coat,
Transfer roll coat, gravure coat, kiss coat, cast coat, spray coat, rod coat, forward rotation roll coat, curtain coat, extrusion coat, bar coat, etc. can be used, and other methods are also possible. The details are described in “Coating Industry” published by Asakura Shoten, pages 253 to 277 (published by Showa 46.3.20). The order of application of these coating liquids can be arbitrarily selected, and a corona discharge treatment or the like may be performed before the application of the desired liquid to improve the adhesion to the undercoat layer or the support. When the magnetic layer or the back layer is desired to be composed of multiple layers, simultaneous multi-layer coating, sequential multi-layer coating or the like may be performed. These are described, for example, in JP-A-57-12.
No. 3532, JP-B-62-37451, JP-A-59-142741, JP-A-59-16523.
No. 9 is disclosed in the specification.

By such a method, about 1 to about
If necessary, the magnetic liquid applied at about 200 μm is dried in multiple stages at 20 to 130 ° C. while the ferromagnetic powder in the layer is immediately dried in a desired direction (vertical, longitudinal, width, random, oblique, etc.) at about 500 to 5000 gauss. ), And the formed magnetic layer is dried to a thickness of 0.1 to 30 μm. The transport speed of the support at this time is usually 10 m / min.
The drying is performed at 900 m / min, the drying temperature is controlled at 20 ° C. to 130 ° C. in the plurality of drying zones, and the amount of residual solvent in the coating film is 0.1 to 40 mg / m ² . The surface of the magnetic layer or the back layer is subjected to a surface smoothing process as necessary, and the center line average surface roughness (Ra) of the magnetic layer or the back layer is set to 0.001 to 0.3 μm (cutoff 0.25 mm). 5 nm
The magnetic recording medium of the present invention is manufactured by setting the Young's modulus of the magnetic layer to less than 1200 Kg / mm ² and cutting it into a desired shape. These production methods include a series of steps of powder pretreatment / surface treatment, kneading / dispersion, coating / orientation / drying, smoothing, heat treatment, radiation irradiation (EB) treatment, surface polishing treatment, cutting, and winding. It is desirable to do. They are,
For example, Japanese Patent Publication No. 40-23625, Japanese Patent Publication No.
No. 28368, JP-B-47-38802, British Patent No. 119191424, JP-B-48-11336, JP-A-49-53631, JP-A-50-1
12005, JP-A-51-77303, JP-B-52-17404, JP-A-60-70532.
Gazette, JP-A-2-265672, U.S. Pat.
No. 473960, and the like. The method disclosed in Japanese Patent Publication No. 41-13181 is considered to be a basic and important technique in this field.

After the magnetic recording medium thus prepared is cut, it is wound on a desired plastic or metal reel.
Immediately before or before winding, it is desirable to burnish and / or clean the magnetic recording medium (magnetic layer, back layer, edge end face, base face). The burnishes the magnetic recording medium with a hard material such as a sapphire blade, a razor blade, a super hard material blade, a diamond blade, or a ceramic blade to smooth the protrusions on the surface of the magnetic recording medium. The Mohs hardness of these materials is preferably 8 or more, but is not particularly limited as long as the protrusions can be removed. The shape of these materials does not need to be a blade in particular, and shapes such as a square shape, a round shape, and a wheel (these materials may be provided around a rotating cylindrical shape) can be used. The magnetic recording medium is cleaned by wiping the magnetic layer surface, the back layer surface, the edge end surface, and the back side base surface with a nonwoven fabric or the like for the purpose of removing dirt and extra lubricant on the surface of the magnetic recording medium. It is done by doing. Examples of such wiping materials include various types of virgin manufactured by Japan Vilene, Toraysee, Exaine, manufactured by Toray, Kimwipe, various polishing tapes manufactured by Fuji Photo Film, and nonwoven fabrics made of nylon nonwoven fabric, polyester nonwoven fabric, rayon Non-woven fabric,
Tissue paper and the like such as acrylonitrile nonwoven fabric and blended nonwoven fabric can be used. These are, for example,
6-39309, JP-B-58-46768, JP-A-56-90429, and JP-B-58-46.
767, JP-A-63-259830, JP-A-1-201824 and the like.

The ferromagnetic powder or non-magnetic powder used in the present invention, binders, additives (lubricants, dispersants, antistatic agents, surface treatment agents, carbon black, abrasives, light shielding agents,
Antioxidants, antifungal agents, etc., solvents and supports (may have an undercoat layer, a back layer, a back undercoat) or a method for producing a magnetic recording medium are described in JP-B-56-26890. You can refer to what you have.

[0053]

EXAMPLES The present invention will be described more specifically with reference to the following examples. It is easily understood by those skilled in the art that the components, ratios, operation orders, and the like shown here can be changed without departing from the spirit of the present invention. Therefore, the present invention should not be limited to the following examples. Parts in Examples are parts by weight.

[Example 1] [I] of the following magnetic layer composition was put into a kneader, kneaded well, and [II] was added. After mixing and dispersing, III was added and dispersed.
A magnetic coating solution was prepared. Magnetic layer composition [I] a. 100 parts of ferromagnetic metal powder (composition: 96% by weight of Fe, 4% by weight of Al) (Hc: 1600 Oe, S _BET : 55 m ² / g, σ _S : 130 emu / g) b. Phenylphosphonic acid 3 parts c. 1 part of phosphoric ester (GAF RE610) d. 8 parts of vinyl chloride resin (Zeon Corporation, MR110) e. Polyurethane resin (Toyobo Co., Ltd., UR8600) 4 parts f. 1 part of polyurethane resin (Toyobo Co., Ltd., Byron 200) g. 8 parts of methyl ethyl ketone h. Lubricant: 0.3 part of tridecyl stearate i. Cyclohexanone 40 parts Here, a is 4% by weight of Al based on the ferromagnetic metal powder.
Is formed, the crystallite size of the oxide film is 30 °, and the crystallite size of the metal part of the ferromagnetic metal powder is 200 °. Also, the ferromagnetic metal powder a
The surface was coated with the organic phosphorus compounds b and c as pretreatment agents.

The components d, e, f and g were used as a mixture. [II]: Dispersion having the following composition Abrasive: 12 parts of α-alumina (average particle size: 0.6 μm: manufactured by Reynolds) Carbon black (Mitsubishi Chemical Corporation, # 3250) 2 parts Polyurethane resin (Toyobo Co., Ltd.) ), UR8300) 2 parts Methyl ethyl ketone 20 parts III Polyisocyanate (Nippon Polyurethane Co., Ltd., C3040) 4 parts Lubricant: 0.3 parts of dibutylamide stearate Lubricant: 0.3 parts of 2-ethylhexyl myristate Lubricant: myristine Acid / palmitic acid (1/1) 0.2 part Lubricant: oleic acid 0.5 part The above polyisocyanate and a lubricant component were mixed.

Methyl ethyl ketone 200 parts After adjusting the viscosity of this magnetic coating solution, a dry coating thickness of 2.0 μm was applied to a 7 μm non-magnetic support polyethylene naphthalate.
μm, and dried while orienting in a magnetic field in the direction of application with a 3000 gauss counter magnet. Then, the following back layer was continuously formed on the surface side of the non-magnetic support provided with the magnetic layer with the composition [I]. Kneading with a kneader machine, [II] is added during the kneading, additional kneading and dispersion are performed, and immediately before coating (within 1 hour),
After the coating liquid prepared by adding I was provided at a thickness of 0.4 μm, the magnetic layer was continuously subjected to metal roll calendering at 100 ° C. three times (processing speed 200 m / min) and slit to 0.5 inch. Thereafter, the magnetic layer was surface-treated with a diamond rotary blade, and cleaned with Toraysee to prepare a tape.

Back layer composition [I] Carbon black (Cabot Co., Ltd., BP800) 100 parts Carbon black (Cancarb Co., Ltd., Thermax) 5 parts Nitrocellulose (Daicel Co., Ltd.) 10 parts Phenoxy resin (UCC) Manufacture, PKHH) 10 parts Polyurethane resin (Nippon Polyurethane, N2301) 25 parts Polyester resin (Toyobo Co., Ltd., Byron 500) 10 parts Dispersant (copper oleate) 0.1 parts Lubricant: phosphate ester (GAF RE610) 2 parts Methyl ethyl ketone 300 parts [II] Carbonate resin (Dainichi Seika, FJ2) 5 parts Abrasives (Sumitomo Chemical Co., Ltd., Hit100) 0.3 parts Barium sulfate (Sakai Chemical, BF1) 0.1 parts Lubricant: dibutyl stearate Amide 0.7 parts Disperse 4 components from carbonate resin to lubricant To.

Lubricant: 2-ethylhexyl myristate 0.7 parts III Polyisocyanate (Nippon Polyurethane Co., Ltd., C3040) 15 parts Methyl ethyl ketone 700 parts This tape was wound into an M2 format cassette 250 m.

[Examples 2 to 4, Comparative Examples 1 to 6] Example 1
A tape was prepared in the same manner as in Example 1 except that the factors described in Table 1 for the ferromagnetic metal powder were changed. In Comparative Example 6, a tape was prepared in the same manner as in Example 1, except that the abrasive α-alumina in Example 1 was changed to 5 parts.

The crystallite size of the ferromagnetic metal powder and oxide film was determined as follows. 1 g of the ferromagnetic metal powder is weighed under a stream of nitrogen and crushed in a mortar. This ferromagnetic metal powder is uniformly packed in a glass plate and measured with an X-ray diffractometer. The diffraction angles and half widths of (220) of 85 to 88 degrees and (110) of 39 to 42 degrees were obtained, and the crystallite size of the ferromagnetic metal powder was obtained. For the crystallite size of the oxide film, the diffraction angle (25 to 50 degrees) and the half width of the iron oxide were determined to determine the crystallite size.

The specific surface area S of the ferromagnetic metal powder
_BET was determined by a nitrogen adsorption method. The properties of the obtained samples were evaluated as follows, and the results are shown in Table 1. Property evaluation Storage RF output = The tape was stored at 40 ° C. and 90% RH for one week, and the level of deterioration was measured with a VTR of M2 in comparison with the tape stored at room temperature (Example 1).

Head contamination = Tape at 40 ° C., 90% RH
For one week, and the head dirt after 50 passes of the M2VTR was evaluated by a three-point method. 3 points: No dirt, 2 points: Dirt, 1 point: Extremely dirty

[0063]

[Table 1]

As is clear from the above table, the present invention achieves both good storage RF output and durability, and is superior to Comparative Examples. Comparative Example 1 is a case where the Al content of the oxide film of the ferromagnetic metal powder is larger than that of the present invention and the crystallite size is large. Comparative Example 2 is that the Al content of the oxide film of the ferromagnetic metal powder is larger than that of the present invention. This is the case where the crystallite size is small and the crystallite size is large.
Comparative Examples 3 and 5 are cases where Al in the oxide film was replaced with Si, and the amount and crystallite size were the same as those of Al. Comparative Example 4 was the same as Comparative Example 3 This is an example in which the child size is increased. In Comparative Example 5, the organic phosphorus compound was omitted. Comparative Example 6 is an example in which the amount of the abrasive is reduced in Example 1, and is inferior in durability. These Comparative Examples 1 to 6,
It can be seen that storage RF output and durability cannot be satisfactorily compatible.

[0065]

The present invention can be produced by optimally blending a ferromagnetic metal powder having a thin oxide film with a known general material, that is, an abrasive, an organic phosphorus compound , and the like. Even after storage under the conditions, high output can be maintained without reducing output and running durability can be ensured, so that an excellent magnetic recording medium can be provided at low cost.

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Tetsuji Nishida 2-2-1-1, Ogimachi, Odawara City, Kanagawa Prefecture Inside Fuji Photo Film Co., Ltd. (56) References JP-A-53-15803 (JP, A) JP-A Sho 63-103424 (JP, A) JP-A-63-142607 (JP, A)

Claims (3)

(57) [Claims] 1. A magnetic recording medium in which a magnetic layer containing a ferromagnetic metal powder, a binder and an abrasive is provided on a non-magnetic support, wherein the surface of the ferromagnetic metal powder contains aluminum, and the content thereof is high. 2 to 5% by weight based on the magnetic metal powder, and the crystallite size of the oxide film of the ferromagnetic metal powder is 15%.
And the magnetic layer is formed of the ferromagnetic metal powder 10.
The magnetic layer contains 10 to 20 parts by weight of an abrasive with respect to 0 parts by weight, and the magnetic layer is represented by the following general formulas (1) to (4).
A magnetic recording medium comprising at least one organic phosphorus compound selected from a compound . (1) (R-O) n PO (OM) 3-n (2) (R-O) n P (OM) 3-n (3) (R) n P (OM) 3-n (4) RPO (OM) ₂ (In each formula, R represents a substituted or unsubstituted alkyl having 6 to 40 carbon atoms.
Kill group, aralkyl group, alkylphenyl group, alkyl
A phenylalkylene oxide group, an alkenyl group, or
M represents a hydrogen atom, an alkali metal or-
N (R ¹ ) ₄ , wherein R ¹ is an alkyl having 1 to 20 carbon atoms
And n represents 1 or 2. ) 2. The magnetic recording medium according to claim 1, wherein both the abrasive and the metal on the surface of the ferromagnetic metal powder are made of a material containing Al atoms. 3. The method according to claim 1, wherein the organic phosphorus compound comprises phenylphosphonic acid and a phosphoric acid ester.
The magnetic recording medium according to the above.