JPH09223615A - Magnetic powder and magnetic recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic powder having a good dispersion property, which ensures the time aging stability to provide a high power, improved durability and is adaptable to high density recordings. SOLUTION: A magnetic powder is treated with two or more different surface treating agents or their solns. one after another in the decreasing order of the area occupied by the molecules of the agent adsorbed to the surface of the powder. One of the treating agents may use omega-hydroxycarboxylic acid or straight-chain carboxylic acid having an unsaturated bond at omega position and the area occupied by other treating agent molecules than the carboxylic acid molecules is preferably larger than that of the carboxylic acid molecules. The powder may be one coated with an organic compd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic powder which is sequentially surface-treated with two or more different surface-treating agents or solutions thereof, and a magnetic recording medium using the same. More specifically, the present invention relates to a magnetic powder having improved dispersibility and temporal stability by defining the treatment order of the surface treatment agent, and a magnetic recording medium using the magnetic powder.

[0002]

2. Description of the Related Art As a magnetic recording medium used in a magnetic recording / reproducing apparatus such as a video tape recorder, a magnetic powder, a binder, an organic solvent, various additives and the like are mixed and dispersed on a non-magnetic support such as a polyester film. The magnetic layer is formed by applying the magnetic coating prepared by the above method, so-called coating type magnetic recording medium or ferromagnetic powder made of metal is directly deposited on the non-magnetic support by vacuum thin film forming technology. A so-called metal thin film type magnetic recording medium in which a magnetic layer is formed by film formation has been proposed, but the former coating type magnetic recording medium is predominant because of its excellent productivity and versatility.

In these magnetic recording media,
It is desired to support high density recording. Therefore, in the above coating type magnetic recording medium, in order to achieve high output,
The magnetic powder in the magnetic layer is made to have an extremely fine particle size, and it is highly dispersed in a binder, and the surface of the magnetic layer is mirror-finished to improve electromagnetic conversion characteristics. It is desired to ensure the stability and improve the stability over time. At the same time, it is desired to improve the durability of the magnetic coating film against sliding of the magnetic head.

[0004]

For this reason, various dispersants for improving dispersibility in order to achieve high output, and highly dispersible binders having a polar group introduced therein have been developed. Furthermore, various rust preventive agents have been developed to secure high magnetization and improve weather resistance in order to improve stability over time.
Further, in the metallic magnetic powder, an iron oxide layer as an antioxidant layer is formed on the surface of the magnetic powder,
A method of treating with an organic compound from a reduced state in which an iron oxide layer is not formed on a metal magnetic powder as disclosed in Japanese Patent Publication No. 089449 has been studied. In addition, various curing agents for crosslinking the binders have been investigated in order to improve durability. However, with these techniques, it is difficult to secure high magnetization of the magnetic powder, to satisfy its dispersibility and weather resistance, and to achieve high output and durability of a magnetic recording medium using this.

On the other hand, as the magnetic powder, Fe has been used in place of the oxide type magnetic powder which has been widely used until now.
Metal magnetic powder mainly composed of is used, and when such a metal magnetic powder is used, weatherability is improved to improve magnetization and dispersibility for higher output and stability with time. It is desired to improve the durability and the durability.

Therefore, the present invention has been proposed in view of the conventional situation, and even if a magnetic metal powder such as Fe as a main component is used as the magnetic powder, high magnetization of the magnetic powder is ensured, and An object of the present invention is to provide a magnetic powder and a magnetic recording medium which have improved dispersibility and stability over time, have higher output, improved durability, and are compatible with high density recording.

[0007]

In order to achieve the above object, the inventors of the present invention have conducted extensive studies over a long period of time, and as a result, when the surface treatment agent is adsorbed on the surface of the magnetic powder by the surface treatment, the magnetic powder It has been found that more effective surface modification can be realized by sequentially performing surface treatment and adsorption in two or more steps starting from a surface treatment agent having a large occupied area of molecules when adsorbed on the surface.

When the surface treatment agent is adsorbed on the surface of the magnetic powder in two or more stages by the surface treatment, the surface treatment agent having the largest occupied area of the molecule when adsorbed is sequentially treated and adsorbed. The following phenomena are thought to occur on the surface of the magnetic powder.

That is, when the surface treatment agent A having the largest occupation area is adsorbed and then treated with the surface treatment agent B having the second largest occupation area, the molecules of the surface treatment agent B are mainly magnetic powder. It is considered that the surface treatment agent A is adsorbed on the unadsorbed portion of the surface. Further, it is considered that when the surface treatment agent C having the second largest occupied area after the surface treatment agent B is treated, the molecules of the surface treatment agent C are mainly adsorbed on the unadsorbed portions of the surface treatment agents A and B on the surface of the magnetic powder. . In this way, the surface treatment agent having the largest occupied area of molecules when adsorbed on the surface of the magnetic powder is sequentially surface-treated and adsorbed, whereby the surface of the magnetic powder can be most efficiently coated with the surface treatment agent. Therefore, the surface of the magnetic powder can be modified most effectively.

Therefore, from the above mechanism, the surface treatment agent having the largest occupied area when adsorbed on the surface of the magnetic powder is adsorbed on the surface of the magnetic powder to the maximum extent, and the unadsorbed portion remaining on the surface of the magnetic powder is next A surface treatment agent having a large occupied area is maximally adsorbed, and a surface treatment agent having the next largest occupied area is also maximally adsorbed to the remaining unadsorbed portion of the magnetic powder surface. It is desirable to determine the amount of each surface treatment agent so that

The occupied area when the surface treatment agent molecules are adsorbed on the surface of the magnetic powder is defined as follows. First, it is approximated that the surface of the magnetic powder is a flat surface in the immediate vicinity of the place where the surface treatment agent molecules are adsorbed, and this is referred to as "a flat surface of the magnetic powder" in the present specification. Then, the functional group in the surface-treating agent molecule is physically or chemically adsorbed on the surface of the magnetic powder by hydrogen bonding, dehydration reaction, or the like, so that the intramolecular energy is minimized with respect to the conformational change of the surface-treating agent molecule. Assuming conformation, the area of the projected image including the van der Waals radius of the surface treatment agent molecule projected on the plane of the magnetic powder at this time is called the occupied area when adsorbed on the surface of the magnetic powder. . Accordingly, the occupied area per mol of the surface treatment agent is defined as a value obtained by multiplying the occupied area when adsorbed on the surface of the magnetic powder by the Avogadro's number.

In order to determine the conformation that minimizes the intramolecular energy of the surface treatment agent molecule with respect to the conformational change, it is necessary to make a trial calculation of the energy level of each atom or ion in the molecule by computer simulation or the like. In some cases, MNDO / AM-1 or MNDO / PM-3 or MND
Any known calculation method such as semi-empirical molecular orbital method including MNDO method such as O / MINDO-3, DV-Xα method, D-MOL method, Gaussian method, and density functional method can be used.

Ideally, the energy of the surface treatment agent molecule is calculated in a state where the functional group is physically and chemically adsorbed on the surface of the magnetic powder by hydrogen bond, dehydration reaction, etc. Atoms or ions on the surface of the magnetic powder near the adsorption site must also be included in the energy calculation target, and depending on the computer, this may not be possible due to the calculation speed, memory capacity, or software calculation method. . In such a case,
The energy state of the surface treatment agent molecule may be approximated by a value calculated in the state of the molecule alone, which is not adsorbed on the surface of the magnetic powder.

That is, the magnetic powder of the present invention is a magnetic powder obtained by sequentially performing surface treatment with two or more different surface treatment agents or their solutions. It is characterized in that surface treatment is performed in order from a surface treatment agent having a large occupied area of the molecule when the molecule is adsorbed on the surface of the magnetic powder.

Further, the magnetic recording medium of the present invention is a magnetic recording medium comprising a non-magnetic support and a magnetic layer containing a magnetic powder and a binder as a main component, wherein the magnetic powder has two or more different surfaces. A surface treatment is sequentially performed with a treatment agent or a solution thereof, and among these surface treatment agents, a surface treatment that has a large occupied area of the molecule when these surface treatment agent molecules are adsorbed on the surface of the magnetic powder. It is characterized in that the surface treatment is applied in order from the agent.

At this time, the magnetic powder may be a magnetic powder in a reduced state to which an organic compound has been previously attached.

Further, in the magnetic powder and the magnetic recording medium of the present invention, one of two or more different surface treatment agents for the magnetic powder is one having a ω-hydroxycarboxylic acid or a linear chain having an unsaturated bond at the ω position. It may be a carboxylic acid.

In this case, when the surface treatment agent molecule other than ω-hydroxycarboxylic acid or linear carboxylic acid having an unsaturated bond at the ω-position is adsorbed on the surface of the magnetic powder, the occupied area is ω-hydroxyl. Carboxylic acid molecule or ω
It is preferable that the linear carboxylic acid molecule having an unsaturated bond at the position is larger than the occupied area when adsorbed on the surface of the magnetic powder.

Further, even in such a case, the magnetic powder may be a magnetic powder in a reduced state to which an organic compound has been previously deposited.

In the magnetic powder and the magnetic recording medium of the present invention, the surface treatment agent may be used as a surface treatment agent for the magnetic powder, and in the case of producing a magnetic coating material, a coating agent together with a binder is used. When converting, it may be added in two or more stages in sequence.

Examples of the magnetic powder suitable as the magnetic powder of the present invention and the magnetic powder of the magnetic recording medium are as follows. For example, ferromagnetic iron oxide, ferromagnetic chromium dioxide, barium ferrite, strontium ferrite, etc. are effective, and further, in order to improve various characteristics, the above ferromagnetic iron oxide is added to Co, Cr, Ni, Mn, Cu, Z.
n, etc. added, or Co, Ni, Fe, Mn, V, Ti, Tc, Ru,
It can be widely applied to those to which elements such as Sn, Ce, Pb, Na and K are added.

Further, ferromagnetic metal materials such as Fe, Co and Ni, Fe-Co, Fe-Ni, Fe-Co-Ni and C are used.
o-Ni, Fe-Mn-Zn, Fe-Ni-Zn, Fe
-Co-Ni-Cr, Fe-Co-Ni-P, Fe-C
F such as o-B, Fe-Co-Cr-B, Fe-Co-V
It is also effective for ferromagnetic metal magnetic powders made of various ferromagnetic alloy materials containing e, Co, and Ni as main components, and for improving these various characteristics, Al, Si,
Any of conventionally known materials such as those to which elements such as Ti, Cr, Mn, Cu, Zn, Mg, P, B and V are added can be applied.

At the production stage of these ferromagnetic metal magnetic powders, a thin iron oxide is formed on the surface of the magnetic powder by gently oxidizing the reduced magnetic powder for the purpose of effectively suppressing the deterioration of the magnetic properties with time. A layer (antioxidant layer) is provided, and such magnetic powder is also applicable as the magnetic powder of the present invention.

In the magnetic powder and the magnetic recording medium of the present invention, as described above, the magnetic powder in which reduced magnetic powder is coated with an organic compound such as an organic rust preventive is also used. It is possible, and in such a magnetic powder, deterioration with time can be effectively suppressed.
The specific surface area of these magnetic powders is arbitrary, but the specific surface area is 1
It is highly effective when applied to those of 0 m ² / g or more, especially 20 m ² / g or more.

The surface treatment agents used for the magnetic powder and the magnetic recording medium of the present invention include conventionally known surface treatment agents, for example, various dispersants and rust preventive agents, which are used in combination. Good. Examples of these dispersants include oxyacids, phosphoric acid esters, amine compounds,
Alkylsulfates, fatty acid amides, higher alcohols, polyethylene oxides, sulfosuccinic acid, sulfosuccinic acid esters, known surfactants and the like, and salts thereof, and also polymer dispersants having a negative organic acid (for example, -COOH) Examples thereof include salt.

Examples of rust preventives include citric acid and its derivatives, phthalic acid and its derivatives, phthalimide and its derivatives, phthalhydrazide and its derivatives, catechol and its derivatives, cyclohexanediol and its derivatives, cyclohexanedicarboxylic acid and Examples thereof include its derivatives, naphthalene diol and its derivatives, naphthalene dicarboxylic acid and its derivatives, and linear monocarboxylic acid having a carboxyl group at its terminal and its derivatives.

Examples of the surface treatment agent as described above include .omega.-hydroxycarboxylic acid and linear carboxylic acid having an unsaturated bond at the .omega. Position as described above. This ω-hydroxycarboxylic acid has a structure represented by HO (CH ₂ ) _n-1 COOH, and n is an integer of 2 or more and 30 or less representing the number of carbon atoms contained in one molecule. On the other hand, a linear carboxylic acid having an unsaturated bond at the ω-position has CH ₂ =
It has a structure of CH (CH ₂ ) _n-3 COOH, and n represents the number of carbon atoms contained in one molecule and is 3 or more and 31 or more.
It is the following integer.

Even when the above-mentioned ω-hydroxycarboxylic acid and linear carboxylic acid having an unsaturated bond at the ω-position are used as the surface treatment agent, they can be used in combination with various dispersants and rust preventives. In this case, the height of the surface treatment agent molecule other than the carboxylic acid from the surface of the magnetic powder when adsorbed on the surface of the magnetic powder is preferably equal to or lower than that of the carboxylic acid.

When ω-hydroxycarboxylic acid and linear carboxylic acid having an unsaturated bond at the ω position are used as the surface treatment agent, the magnetic powder may be one of the above-mentioned Fe, Ferromagnetic metal materials such as Co and Ni, Fe-Co, Fe-Ni, Fe-Co-Ni,
Co-Ni, Fe-Mn-Zn, Fe-Ni-Zn, F
e-Co-Ni-Cr, Fe-Co-Ni-P, Fe-
It is a ferromagnetic metal magnetic powder made of various ferromagnetic alloy materials containing Fe, Co, and Ni as main components, such as Co-B, Fe-Co-Cr-B, and Fe-Co-V. Al, Si, Ti, Cr, M for the purpose of improving characteristics
Those to which elements such as n, Cu, Zn, Mg, P, B and V are added are preferable.

Even when ω-hydroxycarboxylic acid and linear carboxylic acid having an unsaturated bond at the ω position are used as the surface treatment agent, the magnetic powder in the reduced state is used as the magnetic powder as described above. On the other hand, a material coated with an organic compound such as an organic rust preventive agent can be used, and in such a magnetic powder, deterioration with time can be effectively suppressed. The specific surface area of these magnetic powders is preferably 10 m ² / g or more, and more preferably 20 m ² / g or more.

Examples of the method for surface-treating the magnetic powder with the above-mentioned surface treatment agent include, for example, a method of immersing the magnetic powder in a surface treatment agent which is in a liquid state at room temperature, and a surface treatment agent which is solid at room temperature. Examples thereof include a method of immersing the magnetic powder in a treatment liquid dissolved in a solvent, and a method of immersing the magnetic powder after heating and melting. In this case, the solvent of the surface treatment agent is not particularly limited, but water, alcohol solvents such as ethanol, ketone solvents such as acetone and methyl ethyl ketone, ether solvents such as tetrahydrofuran, aromatic solvents such as toluene, etc. Can be used.

The amount of each of these surface treatment agents deposited on the magnetic powder is 100 parts by weight of the magnetic powder.
It is preferably 0.03 to 30 parts by weight, and is obtained by dividing the product of the specific surface area of the magnetic powder and the average molecular weight of the surface treatment agent by 100 by the occupied area per mol of the surface treatment agent described below. It is more preferable that the value is 0.01 to 20 times. If the surface treatment agent is present in excess of the above range, the effect remains unchanged, and the excess amount is wasted. Further, if it is deposited too much, the physical properties of the magnetic coating film of the magnetic recording medium may be adversely affected. On the other hand, if it is less than the above range, that is, if it is 0.03 parts by weight or less, the effect is insufficient and a sufficient effect cannot be obtained.

The magnetic powder of the present invention, which has been surface-treated as described above, is kneaded with a binder, an organic solvent, a lubricant, an abrasive, an antistatic agent and the like to form a magnetic paint, and then a non-magnetic support. The magnetic recording medium of the present invention is obtained by applying the composition onto the magnetic recording layer to form a magnetic layer and subjecting it to a predetermined treatment.

As described above, the magnetic powder is not surface-treated in advance, but the magnetic powder and the above-mentioned surface treatment agent are kneaded together with a binder, an organic solvent and various additives to form a paint. You may make it surface-treat. In this case, the surface treatment agent may be sequentially added to the coating material being kneaded at arbitrary time intervals in two or more stages in descending order of the area occupied by molecules when adsorbed on the surface of the magnetic powder.
The amount of the surface treatment agent added to the paint is the same as the case of the amount of the above-mentioned magnetic powder deposited, and the above-mentioned known dispersants and rust preventives are used in any combination as necessary. You may

Further, in any of the cases where the magnetic powder is surface-treated in advance and the surface treatment is carried out at the time of kneading the magnetic paint, the binder, the organic solvent, and the various additives used are those commonly used in magnetic recording media. Can also be used. Further, in this case, the mixing ratio and the like are set according to the case of a normal magnetic recording medium.

As the above-mentioned binder, those having an average molecular weight of 10,000 to 200,000 are preferable, and the following ones can be mentioned. That is, for example, vinyl chloride-
Vinyl acetate copolymer, vinyl chloride-vinylidene chloride copolymer, vinyl chloride-vinyl acetate-polyvinyl alcohol copolymer, vinyl chloride-acrylonitrile copolymer, polyurethane resin, butadiene-acrylonitrile copolymer, polyamide resin, polyvinyl butyral , Cellulose derivatives (cellulose acetate butyrate, cellulose diacetate, cellulose triacetate, cellulose propionate, nitrocellulose, etc.), styrene-butadiene copolymer, polyester resin, various synthetic rubbers, phenolic resin, epoxy resin, urea resin , Melamine resin, phenoxy resin, silicone resin, acrylic resin, mixture of high molecular weight polyester resin and isocyanate prepolymer, mixture of polyester polyol and polyisocyanate Things, urea formaldehyde resin, mixture of low molecular weight glycol and a high molecular weight diol and isocyanate, and, and mixtures thereof.

These binders are --SO ₃ M, --COO.
M, —PO (OM ′) ₂ (provided that M is hydrogen or an alkali metal such as lithium, potassium and sodium, M ′ is hydrogen, an alkali metal such as lithium, potassium and sodium or a hydrocarbon residue), etc. It may be a resin containing a hydrophilic polar group.

Among the above binder resins, the vinyl chloride type copolymer is a vinyl chloride monomer, a copolymerizable monomer containing an alkali salt of sulfonic acid or phosphoric acid, and various other copolymers if necessary. It can be easily obtained by copolymerizing a functional monomer by vinyl polymerization. This makes it possible to control the polarity of the copolymer arbitrarily.

A hardener may be added as necessary when producing the magnetic paint as described above. Examples of such a curing agent include the following. Polyisocyanate compounds having two or more isocyanate groups such as p-phenylene diisocyanate, tolylene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, isophorone polyisocyanate, polymethylene polyphenylene polyisocyanate, diisocyanate, tolylene diisocyanate, hexa Polyisocyanates such as methylene diisocyanate, tetraglycidyl metaxylenediamine, tetraglycidyl-1,3-bisaminomethylcyclohexane, tetraglycidylaminodiphenylmethane, polyglycidylamine compounds such as triglycidyl-p-aminophenol, 2-dibutyl Amino-
Polythiol compound such as 4,6-dimercapto-substituted triazine, epoxy compound such as triglycidyl isocyanurate, mixture of epoxy compound and isocyanate compound, mixture of epoxy compound and oxazoline compound, mixture of imidazole compound and isocyanate compound, anhydrous methylnazine Any conventionally known acid such as acid can be used. These hardeners are binder 100
It is usually added in the range of 0.2 to 80 parts by weight with respect to parts by weight.

Particularly when ω-hydroxycarboxylic acid is used as the surface treatment agent, one having a hydroxyl group among the above-mentioned binders is used as the binder, and the above-mentioned curing agent is also added. It is preferable that the hydroxyl group of the carboxylic acid and the hydroxyl group in the binder are crosslinked with a curing agent to improve the durability of the magnetic recording medium.

When a straight-chain carboxylic acid having an unsaturated bond at the ω-position is used as the surface treatment agent, a binder having an unsaturated bond is used as the binder.
It is preferable to improve the durability of the magnetic recording medium by crosslinking the unsaturated bonds of the carboxylic acid and the binder.

Examples of such a binder include α rays, β rays,
It is preferable to have a functional group that is crosslinked by radiation such as γ-rays, X-rays, and ultraviolet rays, and have an average molecular weight of 10,000 to 200,000. Examples of this functional group include unsaturated double bonds such as vinyl group, allyl group, acryloyl group, methacryloyl group, acryl group, and methacryl group. Examples of resins having these functional groups include unsaturated groups. Radical polymerization type resin such as polyester type, acrylate type, methacrylate type, radical addition type resin such as polyene-polyol type, cationic polymerization type resin such as epoxy resin,
Further, a vinyl chloride-based binder having an unsaturated bond introduced therein, a urethane-based binder, and the like can be mentioned.

In addition to the above-mentioned binder, various known binders having no unsaturated bond can be used. In this case, the above-mentioned monomer having a functional group is added to the magnetic paint. Therefore, the same effect can be obtained. This monomer includes diacrylic acid esters, acrylic acids, acrylamides, acrylic acid amides,
Acrylic esters, vinyl ethers, vinyl esters, vinyl heterocyclic compounds, N-vinyl compounds, methacrylic acids, methacrylic acid esters, methacrylic acid amides, methacrylamides, allyl compounds, styrenes, olefins, crotons Examples thereof include known substances such as acids and itaconic acids, and mixtures thereof. Of course, these monomers may be used together with a binder having an unsaturated bond without any problem. The amount of addition of these monomers is 100
It is preferably 0.1 to 80 parts by weight with respect to parts by weight.

When it is necessary to add a photopolymerization initiator to crosslink the unsaturated bond, for example, acetophenone, acetophenone diethyl ketal, diacetyl, benzyl, benzyl dimethyl ketal, 1-hydroxycyclohexylphenyl. Ketone, 2
Phenylketones such as hydroxy-2-methylphenylpropanone, benzophenone, bis-4,4'-dialkylaminobenzophenone, 3,3'-dimethyl-4
Benzophenones such as methoxybenzophenone, benzoins, benzoins such as benzoin alkyl ethers, chlorthioxanthone, dimethylthioxanthone,
Xanthones such as diethylthioxanthone, and other known ones such as anthraquinones, sulfides, and phenyloximes can be used alone or as a mixture of two or more kinds. If the addition amount of these polymerization initiators is too small, curing may be insufficient, and if present in excess, it may adversely affect the physical properties of the magnetic coating film of the magnetic recording medium. It is preferably in the range of 0.1 to 50 parts by weight with respect to 100 parts by weight.

Further, in this case, a curing accelerator can be added if necessary. Examples of the curing accelerator include N, N-dimethylethanolamine, N-
Aliphatic amines such as methyldiethanolamine, triethanolamine and tripropanolamine, bis-4,
Aromatic amines such as 4′-dialkylaminobenzophenone and alkyl N, N-dimethylaminobenzoate, and other known amines such as polyamine compounds, alone or
Both can be used as a mixture of two or more kinds. The addition amount of these curing accelerators is preferably in the range of 0.1 to 50 parts by weight with respect to 100 parts by weight of the binder, as in the case of the polymerization initiator.

When the magnetic paint is produced as described above, additives such as a lubricant, an abrasive, a matting agent and an antistatic agent may be added, if necessary.

As the lubricant, silicone oil, graphite, carbon black graphite polymer, molybdenum disulfide, tungsten disulfide, lauric acid, myristic acid, a fatty acid having 12 to 16 carbon atoms and the total number of carbon atoms of the fatty acid are added. A fatty acid ester or the like composed of a monohydric alcohol having 21 to 23 carbon atoms can also be used. These lubricants are usually used in an amount of 0.
It is added in the range of 2 to 20 parts by weight.

As the abrasive, generally used materials include fused alumina, various alumina such as α-alumina, silicon carbide, chromium oxide, corundum, artificial corundum, artificial diamond, garnet, emery and the like. As these abrasives, those having an average particle diameter of 0.05 to 5 μm are used, and particularly preferably 0.1 to 2 μm. These abrasives are usually added to 1 part by weight of 100 parts by weight of the binder.
It is added in the range of ２０20 parts by weight.

As the matting agent, an organic powder or an inorganic powder may be used individually or as a mixture.
The organic powder used in the present invention is preferably acrylic styrene resin powder, benzoguanamine resin powder, melamine resin powder, phthalocyanine pigment, but polyolefin resin powder, polyester resin powder, polyamide resin powder, polyimide resin. Resin powder, polyfluorinated ethylene resin powder and the like can also be used, and as the inorganic powder, silicon oxide, titanium oxide, aluminum oxide, calcium carbonate, barium sulfate, zinc oxide, tin oxide, chromium oxide, silicon carbide, iron oxide, talc, Kaolin, calcium sulfate,
Examples thereof include boron nitride, zinc fluoride, molybdenum dioxide.

Examples of the antistatic agent include carbon black, conductive powders such as graphite, tin oxide-antimony oxide compounds, titanium oxide-tin oxide-antimony oxide compounds, natural surfactants such as saponins, and alkylene oxides. -Based, glycerin-based, glycidol-based, etc. nonionic surfactants, higher alkylamines, quaternary ammonium salts, pyridine, other heterocycles, cation surfactants such as phosphonium or sulfonium, carboxylic acids, sulfonic acids, phosphoric acid Examples thereof include anionic surfactants containing an acidic group such as a sulfuric acid ester group, and amphoteric active agents such as amino acids, aminosulfonic acids, sulfuric acid or phosphoric acid esters of amino alcohols.

As the solvent to be added to the above paint, or a diluting solvent at the time of applying this paint, ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, alcohols such as methanol, ethanol, propanol, butanol, acetic acid, etc. Methyl, ethyl acetate, butyl acetate, ethyl lactate, esters such as ethylene glycol monoacetate, ethers such as glycol dimethyl ether, glycol monoethyl ether, dioxane and tetrahydrofuran, aromatic hydrocarbons such as benzene, toluene and xylene, methylene chloride , Ethylene chloride, carbon tetrachloride, chloroform,
Halogenated hydrocarbons such as dichlorobenzene can be used.

Examples of the non-magnetic support used in the magnetic recording medium of the present invention include the following. Polyethylene terephthalate, polyethylene naphthalate,
Examples thereof include polyesters such as polyethylene-2,6-naphthalate, polyolefins such as polypropylene, cellulose derivatives such as cellulose triacetate and cellulose diacetate, and plastics such as polyamide and polycarbonate. Metals such as copper, aluminum and zinc, and glass. Ceramics of boron nitride, silicon carbide, etc. can also be used.

The thickness of these non-magnetic supports is a film,
In the case of a sheet, it is about 3 to 100 μm, preferably 5
~ 50μm, 30μ in the case of disk or card
It is about m to 10 mm, and in the case of a drum shape, it is used in a cylindrical shape, and its shape is determined according to the recorder used. An intermediate layer for improving adhesiveness may be provided between the non-magnetic support and the magnetic layer.

As a coating method for coating the above magnetic coating material on a non-magnetic support, air doctor coating, blade coating, air knife coating, squeeze coating, impregnation coating, reverse roll coating, transfer roll coating, gravure coating , Kiss coat, cast coat, spray coat, extrusion coat and the like can be used, but not limited thereto. When the magnetic layer is formed on the non-magnetic support by these coating methods, a method of stacking the coating and drying steps one by one and a method of successively coating the next layer on the undried wet layer However, either method may be used.

The magnetic coating material coated on the non-magnetic support by such a method is used in the coating material (in the magnetic layer) as needed.
After the magnetic powder is oriented, it is dried.
In this case, the orientation magnetic field is about 500 to 500 AC or DC.
It is about 0 gauss, the drying temperature is about 50 to 120 ° C., and the drying time is about 0.1 to 10 minutes. If necessary, the surface is smoothed or cut into a desired shape to manufacture a magnetic recording medium.

Even when ω-hydroxycarboxylic acid is used as the surface treatment agent, the formed magnetic layer is subjected to a treatment for orienting the magnetic powder in the magnetic layer, if necessary, and then dried. In this case, the orienting magnetic field is about 500 to 5000 gauss with AC or DC, the drying temperature is about 50 to 120 ° C., and the drying time is about 0.1 minute to 2
It is about 00 hours. In this drying step, the crosslinking reaction between the hydroxyl group in ω-hydroxycarboxylic acid and the hydroxyl group in the binder is also accelerated.

When a straight-chain carboxylic acid having an unsaturated bond at the ω-position is used as the surface treatment agent and an unsaturated bond is used as the binding agent, it is necessary for the formed magnetic layer. The magnetic powder in the magnetic layer is accordingly oriented, and the formed magnetic layer is dried and irradiated with radiation to bond the molecules of the binder with each other and the linear carbon atom having an unsaturated bond at the ω-position. Crosslinks and cures between the unsaturated bond of the acid and the unsaturated bond of the binder.

The radiation to be applied is α ray, β
Among the rays, γ rays, X rays, ultraviolet rays and the like, those suitable for polymerization by the unsaturated bond introduced into the binder may be used. For example, an electron beam accelerator or the like can be used as an electron beam source, an X-ray generator as an X-ray source, and a mercury lamp, a chemical lamp, a metal halide lamp, an arc as an ultraviolet ray source. A lamp, a xenon lamp, etc. can be mentioned. Further, an arbitrary cooling device or the like may be used together for the purpose of preventing the temperature rise of the magnetic recording medium due to the irradiation of radiation.

The coating material on the non-magnetic support is dried before or after the above-mentioned radiation curing. At this time, the drying temperature is about 50 to 120 ° C. and the drying time is about 0.1 to 1.
It takes about 0 minutes. Further, the orientation magnetic field at the time of orientation is about 500 to 5000 gauss with AC or DC.

In the magnetic powder and the magnetic recording medium of the present invention, the magnetic powder is sequentially surface-treated with two or more kinds of different surface treatment agents or their solutions. Of these surface treatment agents, Since these surface treatment agents are subjected to surface treatment in order from the surface treatment agent having the largest occupied area of the molecule when adsorbed on the surface of the magnetic powder, the surface treatment agent has the largest occupied area. After adsorbing the first surface treatment agent on the magnetic powder, the second surface treatment agent having a large occupied area is adsorbed on the non-adsorbed portion of the first surface treatment agent, following the first surface treatment agent. This means that various surface treatment agents are efficiently applied to the surface of the magnetic powder. Therefore, in the magnetic powder and the magnetic recording medium of the present invention, the dispersibility and weather resistance can be effectively improved by selecting the type of the surface treatment agent for the magnetic powder.

In this case, by adsorbing two or more kinds of dispersants, a magnetic powder having more excellent dispersibility is prepared, and in this case, by adsorbing two or more kinds of rust preventive agents, weather resistance is improved. A magnetic powder having excellent properties is prepared.

At this time, if the magnetic powder is formed by previously depositing an organic compound on the reduced magnetic powder, a high magnetization of the magnetic powder is ensured and the stability over time is further improved.

In the magnetic powder and magnetic recording medium of the present invention, one of two or more different surface treatment agents may be ω-hydroxycarboxylic acid or linear carboxylic acid having an unsaturated bond at the ω position. For example, the carboxyl groups in these carboxylic acids are adsorbed on the surface of the magnetic powder and the active sites on the surface of the magnetic powder lose their activity, so that the weather resistance of the magnetic powder is improved.

Further, when the surface treating agent as described above is used, when the magnetic powder of the present invention is used as a magnetic coating material, the magnetic powder is formed by the affinity between the alkyl chain in the carboxylic acid and the binder or the organic solvent. A high dispersibility in the binder is obtained, and the dispersibility of the magnetic powder in the magnetic layer of the magnetic recording medium of the present invention is good.

[0065]

EXAMPLES Preferred examples of the present invention will be described below based on experimental results, but it goes without saying that the present invention is not limited to the examples shown below.

<Experimental Example 1> In this experimental example, in a magnetic powder obtained by sequentially performing surface treatment with two or more different surface treatment agents or solutions thereof, among these surface treatment agents, these surface treatment agents are used. An example of the magnetic powder of the present invention in which the surface treatment is performed in order from the surface treatment agent having the largest occupied area of the molecule when the agent molecules are adsorbed on the surface of the magnetic powder and the magnetic recording medium of the present invention using the same will be described. That is, a magnetic powder not subjected to surface treatment and Comparative Example 1 which is a magnetic recording medium using the magnetic powder, and a magnetic powder subjected to surface treatment in order from one having a smaller occupied area of two or more different surface treatment agents, and the magnetic powder Comparative Examples 2 and 3 which are magnetic recording media used, magnetic powders which have been surface-treated in order from the one having a larger occupied area of two or more different surface treatment agents, and Example 1 which is a magnetic recording medium using the same. Nos. 10 to 10 were manufactured and their magnetic properties, surface gloss and stability over time were investigated. The manufacturing process of each magnetic powder and the magnetic recording medium and the experimental results are shown below together.

COMPARATIVE EXAMPLE 1 In this example , commercially available magnetic powder of needle-shaped metallic iron magnetic powder for magnetic recording (specific surface area 53.9 m ² / g, coercive force Hc = 1)
26.5 kA / m, saturation magnetization σs = 120 Am ² / k
g, average major axis length 0.3 μm, acicular ratio 8 to 10) to prepare a magnetic recording medium. This magnetic powder and magnetic recording medium will be referred to as Comparative Example 1 for convenience.

That is, a magnetic coating material having the following composition was prepared, applied onto a polyester base film having a thickness of 30 μm, oriented with an orientation magnetic field of 5000 gauss, and then dried at 60 ° C. for 5 minutes. A magnetic tape was produced as a magnetic recording medium.

Needle metal iron magnetic powder for magnetic recording 100 parts by weight Vinyl chloride / vinyl acetate copolymer 10 parts by weight Polyurethane resin 10 parts by weight Carbon 3 parts by weight Aluminum oxide 2 parts by weight Polyisocyanate 5 parts by weight Methyl ethyl ketone 100 parts by weight Toluene 100 50 parts by weight Cyclohexanone 50 parts by weight The magnetic characteristics of the magnetic recording medium thus obtained were measured by a vibrating sample type magnetometer, and the surface glossiness was measured by a standard gloss meter as total reflectance. The measurement value of the surface glossiness indicating the surface glossiness was normalized by setting the measurement value of this Comparative Example 1 to 100%. The stability with time was determined by measuring the deterioration rate (aging with time) of the residual magnetic flux density when the magnetic recording medium was left in an environment of a temperature of 60 ° C. and a relative humidity of 90% for 7 days. The above measured values are shown in Table 1. In addition, Comparative Examples 2 and 3 and Examples 1 to 10 described later.
The results are also shown in Table 1.

[0070]

[Table 1]

Comparative Example 2 In this example, a magnetic powder obtained by subjecting the magnetic powder of Comparative Example 1 to surface treatment twice was prepared, and a magnetic recording medium was produced by the same method as in Comparative Example 1 using this magnetic powder. The magnetic powder and the magnetic recording medium are referred to as Comparative Example 2 for convenience.

The magnetic powder of Comparative Example 2 is shown in Comparative Example 1.
First, CH_Three (CH_Two )₁₄CO
0.6 mol / l of palmitic acid having the structure of OH
Immerse a specified amount of the above magnetic powder in a tanol solution and vibrate.
After shaking in the mill for 3 hours, only the magnetic powder was filtered and separated.
And dried in air. Further, C₆ H_Four (COOH) _Two 
Of phthalic acid having the structure of 0.3 mol / l ethanol
Dip a specified amount of the above magnetic powder into the solution and use a vibration mill to
After shaking for a long time, only the magnetic powder is filtered and separated in the air.
And dried. That is, in this Comparative Example 2, the surface
Surface treatment agent when it is adsorbed on the surface of magnetic powder
Use magnetic powders in order from the one with the smallest molecule occupation area.
The surface was treated.

Then, using the magnetic powder of Comparative Example 2, a magnetic tape was manufactured as a magnetic recording medium in the same manner as in Comparative Example 1, and the magnetic properties, surface glossiness and temporal stability were the same as in Comparative Example 1. It was measured. The results are also shown in Table 1.

Comparative Example 3 In this example, a magnetic powder obtained by subjecting the magnetic powder of Comparative Example 1 to surface treatment three times was prepared, and a magnetic recording medium was produced by the same method as in Comparative Example 1 using this magnetic powder. The magnetic powder and the magnetic recording medium are referred to as Comparative Example 3 for convenience.

The magnetic powder of Comparative Example 3 was prepared by comparing the magnetic powder of Comparative Example 1 with CH ₃ (CH ₂ ) ₁₄ CO.
A predetermined amount of the above magnetic powder was immersed in a 0.4 mol / l ethanolic solution of palmitic acid having an OH structure, shaken in a vibration mill for 3 hours, and then only the magnetic powder was filtered, separated, and dried in the atmosphere. Then C ₆ H ₄ (COOH) ₂
A predetermined amount of the above magnetic powder is dipped in a 0.2 mol / l ethanol solution of phthalic acid having the structure shown in FIG.
After shaking for a period of time, only the magnetic powder was filtered, separated and dried in the atmosphere. Further, a predetermined amount of the above magnetic powder was immersed in a 0.2 mol / l ethanol solution of 1,8-naphthalic anhydride having a structure of C ₁₂ H ₆ O ₃ and shaken in a vibration mill for 3 hours. Was filtered, separated and dried in air. That is, in Comparative Example 3, the surface treatment agent was used in order from the surface treatment agent having the smallest occupied area of the surface treatment agent molecule when adsorbed on the surface of the magnetic powder to perform the surface treatment of the magnetic powder.

Then, using the magnetic powder of Comparative Example 3, a magnetic tape was manufactured as a magnetic recording medium in the same manner as in Comparative Example 1, and the magnetic characteristics, surface glossiness and temporal stability were the same as in Comparative Example 1. It was measured. The results are also shown in Table 1.

Example 1 In this example , the same kind of surface treatment agent as that used in the magnetic powder of Comparative Example 2 was used, and the treatment order of these surface treatment agents was changed to obtain the magnetic powder of Comparative Example 1. A magnetic powder subjected to surface treatment was prepared, and this magnetic powder was used to prepare a magnetic recording medium in the same manner as in Comparative Example 1. The magnetic powder and the magnetic recording medium are referred to as Example 1 for convenience.

This magnetic powder of Example 1 was prepared by first adding a predetermined amount of the magnetic powder of Comparative Example 1 to a 0.3 mol / l ethanol solution of phthalic acid having a structure of C ₆ H ₄ (COOH) _2. The above magnetic powder of 1 was soaked and shaken in a vibration mill for 3 hours, then only the magnetic powder was filtered, separated and dried in the atmosphere. Then, a predetermined amount of the magnetic powder was immersed in a 0.6 mol / l ethanol solution of palmitic acid having a structure of CH ₃ (CH ₂ ) ₁₄ COOH, and the magnetic powder alone was filtered after shaking for 3 hours in a vibration mill. Separated and dried in air. That is, in this Example 1, the surface treatment was performed in order from the surface treatment agent having the largest occupied area of the surface treatment agent molecule when adsorbed on the surface of the magnetic powder.

Then, using the magnetic powder of Example 1, a magnetic tape was manufactured as a magnetic recording medium in the same manner as in Comparative Example 1, and the magnetic properties, surface glossiness and temporal stability were the same as in Comparative Example 1. It was measured. The results are also shown in Table 1.

As shown in the results of Table 1, this Example 1
It is clear that the magnetic recording medium of No. 1 has high surface gloss, residual magnetic flux density, and squareness ratio, and has high dispersibility as compared with Comparative Examples 1 to 3. Further, in Example 1, the stability over time is good, which is considered to be because the surface treatment agent is effectively adsorbed to the active sites on the surface of the magnetic powder, and as a result, the weather resistance of the magnetic powder is improved. .

This shows the usefulness of the magnetic powder obtained by sequentially treating the surface of the magnetic powder in two or more times from the surface treatment agent having a large occupied area of molecules when adsorbed on the surface of the magnetic powder as a magnetic material. Is.

Example 2 In Example 1 above, a magnetic coating material was prepared by using a magnetic powder that had been surface-treated twice in advance to prepare a magnetic recording medium. Without the surface treatment, the magnetic powder of Comparative Example 1 and two kinds of surface treatment agents are sequentially added to the magnetic coating material to perform the surface treatment of the magnetic powder to produce the magnetic powder and prepare the magnetic coating material. Then, this was coated on a non-magnetic support in the same manner as in Comparative Example 1 to prepare a magnetic recording medium. The magnetic powder and the magnetic recording medium are referred to as Example 2 for convenience.

The magnetic powder of Example 2 is subjected to a surface treatment when a magnetic coating material having the composition shown in Comparative Example 1 is prepared using the magnetic powder of Comparative Example 1 which has not been surface treated. However, in this Example 2, 3 parts by weight of phthalic acid was added at the same time as the addition of the magnetic powder, and 6 parts by weight of palmitic acid was added at the time when half of the total kneading time had passed, as described above, during the preparation of the magnetic coating material. Added additionally. As a result, phthalic acid and palmitic acid are sequentially adsorbed on the surface of the magnetic powder during the kneading of the magnetic coating material, and the surface treatment of the magnetic powder is performed to obtain the magnetic powder of Example 2. Then, using the magnetic coating material containing the magnetic powder of Example 2, a magnetic tape was manufactured as a magnetic recording medium in the same manner as in Comparative Example 1.

Then, the magnetic characteristics, surface glossiness and temporal stability of this magnetic recording medium were measured in the same manner as in Comparative Example 1. The results are also shown in Table 1.

As shown in the results of Table 1, this Example 2
It was confirmed that the magnetic recording medium of No. 1 also ensures high dispersibility and high stability over time (weather resistance), as in Example 1.

This means that when a magnetic coating material is prepared, a surface treatment agent having a large occupied area of molecules when adsorbed on the surface of the magnetic powder is sequentially added in two or more times, which is an excellent surface for the magnetic powder. It shows the processability.

Example 3 Here, the same kind of surface treatment agent as used in the magnetic powder of Comparative Example 2 and HO (CH ₂ ) ₁₅ COO were used.
Using 16-hydroxypalmitic acid having a structure of H, and changing the treatment order of these surface treatment agents, magnetic powder of Comparative Example 1 subjected to surface treatment was prepared, and the magnetic powder was used. A magnetic recording medium was manufactured by the same method as in Comparative Example 1. The magnetic powder and the magnetic recording medium are referred to as Example 3 for convenience.

The magnetic powder of this Example 3 was prepared by comparing the powder of Comparative Example 1 with a predetermined amount of phthalic acid having a structure of C ₆ H ₄ (COOH) ₂ in a 0.3 mol / l ethanol solution. The magnetic powder was immersed, shaken in a vibration mill for 3 hours, and then only the magnetic powder was filtered, separated, and dried in the atmosphere. Then, a 0.4 mol / l ethanol solution of palmitic acid having a structure of CH ₃ (CH ₂ ) ₁₄ COOH and H 2
A predetermined amount of the magnetic powder was immersed in a mixed solution of a 0.2 mol / l ethanol solution of 16-hydroxypalmitic acid having a structure of O (CH ₂ ) ₁₅ COOH, and the mixture was shaken with a vibration mill for 3 times.
After shaking for a period of time, only the magnetic powder was filtered, separated and dried in the atmosphere. That is, in this Example 3, the surface treatment was performed in order from the surface treatment agent having the largest occupied area of the surface treatment agent molecule when adsorbed on the surface of the magnetic powder. In addition, in the case of the second surface treatment, a mixture of two organic compounds having substantially the same occupied area and chain length was used.

Next, 0.4 mol / l of naphthalic anhydride
A predetermined amount of the above magnetic powder was immersed in an ethanol solution, shaken in a vibration mill for 3 hours, and then only the magnetic powder was filtered, separated, and dried in the atmosphere. Furthermore, 0.2 of myristic acid
A predetermined amount of the above magnetic powder was immersed in a mol / l ethanol solution, shaken in a vibration mill for 3 hours, and then only the magnetic powder was filtered, separated, and dried in the atmosphere. That is, in this Example 11, the surface treatment was performed in order from the surface treatment agent having the largest occupied area of the surface treatment agent molecule when adsorbed on the surface of the magnetic powder.

Then, using the magnetic powder of Example 3, a magnetic tape was manufactured as a magnetic recording medium in the same manner as in Comparative Example 1, and the magnetic characteristics, surface glossiness and temporal stability were the same as in Comparative Example 1. It was measured. The results are also shown in Table 1.

As shown in the results of Table 1, this Example 3
It is clear that the magnetic recording medium of No. 1 has high surface gloss, residual magnetic flux density, and squareness ratio, and has high dispersibility as compared with Comparative Examples 1 to 3. Further, in Example 3, the stability over time is good, which is considered to be because the surface treatment agent is effectively adsorbed to the active sites on the surface of the magnetic powder, and as a result, the weather resistance of the magnetic powder is improved. .

This shows the usefulness of the magnetic powder, which has been subjected to the surface treatment successively in two or more times from the surface treatment agent having a large occupied area of molecules when adsorbed on the surface of the magnetic powder, as a magnetic material. Is.

Example 4 In Example 3 above, a magnetic coating material was prepared by using magnetic powder that had been surface-treated twice in advance to prepare a magnetic recording medium. The magnetic powder of Comparative Example 1 and the three kinds of surface treatment agents were sequentially added to the magnetic coating material in two steps without surface treatment, and the surface treatment of the magnetic powder was performed to produce the magnetic powder. A magnetic coating material was prepared and coated on a non-magnetic support in the same manner as in Comparative Example 1 to prepare a magnetic recording medium. The magnetic powder and the magnetic recording medium are referred to as Example 4 for convenience.

The magnetic powder of Example 4 is subjected to surface treatment when a magnetic coating material having the composition shown in Comparative Example 1 is prepared using the magnetic powder of Comparative Example 1 which has not been surface-treated. However, in this Example 4, 3 parts by weight of phthalic acid was added at the same time as the addition of the magnetic powder, and 4 parts by weight of palmitic acid was added at the time when half of the total kneading time had passed, as described above, during the preparation of the magnetic coating material. 2 parts by weight of 16-hydroxypalmitic acid was additionally added. As a result, phthalic acid, palmitic acid and 16-hydroxypalmitic acid are sequentially adsorbed on the surface of the magnetic powder during the kneading of the magnetic coating material, and the surface treatment of the magnetic powder is performed, whereby the magnetic powder of Example 4 is obtained. Then, using the magnetic coating material containing the magnetic powder of Example 4, a magnetic tape was manufactured as a magnetic recording medium in the same manner as in Comparative Example 1.

Then, the magnetic characteristics, surface glossiness and temporal stability of this magnetic recording medium were measured in the same manner as in Comparative Example 1. The results are also shown in Table 1.

As shown in the results of Table 1, this Example 4
It was confirmed that in the magnetic recording medium of No. 3, high dispersibility and high stability over time (weathering resistance) were secured as in Example 3.

This means that when a magnetic coating material is prepared, a surface treatment agent having a large occupied area of molecules when adsorbed on the surface of the magnetic powder is sequentially added in two or more times, which is an excellent surface for the magnetic powder. It shows the processability.

Example 5 In this example, a magnetic powder obtained by subjecting the magnetic powder of Comparative Example 1 to surface treatment twice was prepared, and a magnetic recording medium was produced by the same method as in Comparative Example 1 using this magnetic powder. The magnetic powder and the magnetic recording medium are referred to as Example 5 here for convenience.

The magnetic powder of Example 5 was prepared by subjecting the magnetic powder of Comparative Example 1 to a solution of phthalic anhydride having a structure of C ₈ H ₄ O ₃ in a 0.3 mol / l ethanol solution. A certain amount of the above magnetic powder was immersed, shaken in a vibration mill for 3 hours, and then only the magnetic powder was filtered, separated, and dried in the atmosphere. Next, a 0.4 mol / l ethanol solution of myristic acid having a structure of CH ₃ (CH ₂ ) ₁₂ COOH and HO
A predetermined amount of the magnetic powder was immersed in a mixed solution of a 0.1 mol / l ethanol solution of 12-hydroxylauric acid having a structure of (CH ₂ ) ₁₁ COOH, and after shaking for 3 hours in a vibration mill, only the magnetic powder was removed. It was filtered, separated and dried in air. That is, in this Example 5, the surface treatment was performed in order from the surface treatment agent having the largest occupied area of the surface treatment agent molecule when adsorbed on the surface of the magnetic powder. A mixture of two organic compounds having substantially the same occupied area and different chain lengths was used for the second surface treatment.

Then, using the magnetic powder of Example 5, a magnetic tape was manufactured as a magnetic recording medium in the same manner as in Comparative Example 1, and the magnetic properties, surface glossiness and temporal stability were the same as in Comparative Example 1. It was measured. The results are also shown in Table 1.

As shown in the results of Table 1, this Example 5
It is clear that the magnetic recording medium of No. 1 has high surface gloss, residual magnetic flux density, and squareness ratio, and has high dispersibility as compared with Comparative Examples 1 to 3. In addition, in Example 5, the stability over time is good, which is considered to be because the surface treatment agent is effectively adsorbed to the active sites on the surface of the magnetic powder, and as a result, the weather resistance of the magnetic powder is improved. .

This shows the usefulness of the magnetic powder which has been subjected to the surface treatment successively in two or more times from the surface treatment agent having a large occupied area of molecules when adsorbed on the surface of the magnetic powder as a magnetic material. Is.

Example 6 In Example 5, the magnetic coating material was prepared by using the magnetic powder which had been surface-treated twice in advance to prepare the magnetic recording medium. The magnetic powder of Comparative Example 1 and the three kinds of surface treatment agents were sequentially added to the magnetic coating material in two steps without surface treatment, and the surface treatment of the magnetic powder was performed to produce the magnetic powder. A magnetic coating material was prepared and coated on a non-magnetic support in the same manner as in Comparative Example 1 to prepare a magnetic recording medium. The magnetic powder and the magnetic recording medium are referred to as Example 6 for convenience.

The magnetic powder of Example 6 is subjected to surface treatment when a magnetic coating material having the composition shown in Comparative Example 1 is prepared by using the magnetic powder of Comparative Example 1 which has not been surface-treated. However, in Example 6, 3 parts by weight of phthalic anhydride was added at the same time as the introduction of the magnetic powder, and 4 parts by weight of myristic acid was added at the time when half the total kneading time had elapsed, when the magnetic coating material was prepared, as described above. And 12-hydroxylauric acid 1
Added by weight and. As a result, phthalic anhydride, myristic acid and 12-hydroxylauric acid are sequentially adsorbed on the surface of the magnetic powder during the kneading of the magnetic coating material, and the surface treatment of the magnetic powder is performed to obtain the magnetic powder of Example 6.
Then, using the magnetic coating material containing the magnetic powder of Example 6, a magnetic tape was manufactured as a magnetic recording medium in the same manner as in Comparative Example 1.

Then, the magnetic characteristics, surface glossiness and temporal stability of this magnetic recording medium were measured in the same manner as in Comparative Example 1. The results are also shown in Table 1.

As shown in the results of Table 1, this Example 6
It was confirmed that high magnetic dispersibility and high temporal stability (weathering resistance) can be ensured also in the magnetic recording medium of.

This means that when a magnetic coating material is prepared, a surface treatment agent having a large occupied area of molecules when adsorbed on the surface of the magnetic powder is sequentially added in two or more times, which is an excellent surface for the magnetic powder. It shows the processability.

Example 7 In this example , the same type of surface treatment agent as that used in the magnetic powder of Comparative Example 3 was used, and the treatment order of these surface treatment agents was changed to obtain the magnetic powder of Comparative Example 1. A magnetic powder subjected to surface treatment was prepared, and this magnetic powder was used to prepare a magnetic recording medium in the same manner as in Comparative Example 1. The magnetic powder and the magnetic recording medium are referred to as Example 7 for convenience.

The magnetic powder of Example 7 was obtained by comparing the magnetic powder of Comparative Example 1 with 0.2 mol / l ethanol of 1,8-naphthalic anhydride having a structure of C ₁₂ H ₆ O _3. A predetermined amount of the magnetic powder was immersed in the solution, shaken in a vibration mill for 3 hours, and then only the magnetic powder was filtered, separated, and dried in the atmosphere. Then, a predetermined amount of the magnetic powder was immersed in a 0.2 mol / l ethanol solution of phthalic acid having a structure of C ₆ H ₄ (COOH) ₂ and shaken in a vibration mill for 3 hours, and then only the magnetic powder was filtered, Separated and dried in air. Further, a predetermined amount of the magnetic powder was immersed in a 0.4 mol / l ethanol solution of palmitic acid having a structure of CH ₃ (CH ₂ ) ₁₄ COOH, and the magnetic powder alone was filtered after shaking with a vibration mill for 3 hours. Separated and dried in air. That is, in this Example 7, the surface treatment was performed in order from the surface treatment agent having the largest occupied area of the surface treatment agent molecule when adsorbed on the surface of the magnetic powder.

Then, using the magnetic powder of Example 7, a magnetic tape was manufactured as a magnetic recording medium in the same manner as in Comparative Example 1, and the magnetic properties, surface glossiness and temporal stability were the same as in Comparative Example 1. It was measured. The results are also shown in Table 1.

As shown in the results of Table 1, this Example 7
It is clear that the magnetic recording medium of No. 1 has high surface gloss, residual magnetic flux density, and squareness ratio, and has high dispersibility as compared with Comparative Examples 1 to 3. In addition, in Example 7, the stability over time was good, which is considered to be because the surface treatment agent was effectively adsorbed to the active sites on the surface of the magnetic powder, and as a result, the weather resistance of the magnetic powder was improved. .

This indicates the usefulness of the magnetic powder, which has been subjected to the surface treatment successively in two or more times from the surface treatment agent having a large occupied area of the molecule when adsorbed on the surface of the magnetic powder, as a magnetic material. Is.

Example 8 In Example 7, the magnetic coating material was prepared by using the magnetic powder which had been subjected to the surface treatment three times in advance to prepare the magnetic recording medium. Without performing the surface treatment, the magnetic powder of Comparative Example 1 and three kinds of surface treatment agents are sequentially added to the magnetic coating material to perform the surface treatment of the magnetic powder to produce the magnetic powder and prepare the magnetic coating material. Then, this was coated on a non-magnetic support in the same manner as in Comparative Example 1 to prepare a magnetic recording medium. The magnetic powder and the magnetic recording medium are referred to as Example 8 for convenience.

The magnetic powder of Example 8 is to be surface-treated when a magnetic coating material having the composition shown in Comparative Example 1 is prepared using the magnetic powder of Comparative Example 1 which has not been surface-treated. However, in Example 8, 2 parts by weight of 1,8-naphthalic anhydride was added at the same time as the addition of the magnetic powder during the preparation of the magnetic coating material, and then one-third of the total kneading time passed. At that point, 2 parts by weight of phthalic acid was added, and when one-third of the total kneading time had elapsed, palmitic acid 4
An additional weight part was added. As a result, 1,8-naphthalic anhydride, phthalic acid and palmitic acid were sequentially adsorbed on the surface of the magnetic powder during the kneading of the magnetic coating material, and the surface treatment of the magnetic powder was performed to obtain the magnetic powder of Example 8. . Then
A magnetic tape was manufactured as a magnetic recording medium in the same manner as in Comparative Example 1 using the magnetic coating material containing the magnetic powder of Example 8.

Then, the magnetic characteristics, surface glossiness, and temporal stability of this magnetic recording medium were measured in the same manner as in Comparative Example 1. The results are also shown in Table 1.

As shown in the results of Table 1, this Example 8
It was confirmed that also in the magnetic recording medium of No. 3, high dispersibility and high stability over time (weather resistance) were secured as in Example 7.

This means that when a magnetic coating material is prepared, a surface treatment agent having a large occupied area of molecules when adsorbed on the surface of the magnetic powder is sequentially added in two or more times, which is an excellent surface for the magnetic powder. It shows the processability.

Example 9 Here, a surface treatment agent of substantially the same kind as the surface treatment agent used in Comparative Example 3 and myristic acid having a structure of CH ₃ (CH ₂ ) ₁₂ COOH, HO (CH ₂ ) ₁₁ COOH, were used. A magnetic powder obtained by subjecting the magnetic powder of Comparative Example 1 to surface treatment by using 12-hydroxylauric acid having a structure and changing the treatment order of these surface treatment agents was prepared. A magnetic recording medium was produced in the same manner as in 1. The magnetic powder and magnetic recording medium are referred to as Example 9 for convenience.

The magnetic powder of Example 9 was prepared by comparing the magnetic powder of Comparative Example 1 with 0.2 mol / l ethanol of 1,8-naphthalic anhydride having a structure of C ₁₂ H ₆ O _3. A predetermined amount of the magnetic powder was immersed in the solution, shaken in a vibration mill for 3 hours, and then only the magnetic powder was filtered, separated, and dried in the atmosphere. Next, a predetermined amount of the above magnetic powder was immersed in a 0.2 mol / l ethanol solution of phthalic anhydride having a structure of C ₈ H ₄ O ₃ and shaken in a vibration mill for 3 hours, and then only the magnetic powder was filtered and separated. And dried in air. Furthermore, 0.3 mol / l ethanol solution of myristic acid having a structure of CH ₃ (CH ₂ ) ₁₂ COOH, and H
A predetermined amount of the above magnetic powder was immersed in a mixed solution of 0.1 mol / l ethanol solution of 12-hydroxylauric acid having a structure of O (CH ₂ ) ₁₁ COOH, and after shaking for 3 hours in a vibration mill, only the magnetic powder was obtained. Was filtered, separated and dried in air. That is, in this Example 9, the surface treatment was performed by using the surface treatment agents in order from the one having the largest occupied area of the surface treatment agent molecule when adsorbed on the surface of the magnetic powder. Note that a mixture of two organic compounds having almost the same occupied area was used for the third surface treatment.

Then, using the magnetic powder of Example 9, a magnetic tape was manufactured as a magnetic recording medium in the same manner as in Comparative Example 1, and the magnetic properties, surface glossiness and temporal stability were the same as in Comparative Example 1. It was measured. The results are also shown in Table 1.

As shown in the results of Table 1, this Example 9
It is clear that the magnetic recording medium of No. 1 has high surface gloss, residual magnetic flux density, and squareness ratio, and has high dispersibility as compared with Comparative Examples 1 to 3. In addition, in Example 9, the stability over time is good, which is considered to be because the surface treatment agent is effectively adsorbed to the active sites on the surface of the magnetic powder, and as a result, the weather resistance of the magnetic powder is improved. .

This shows the usefulness of the magnetic powder obtained by sequentially treating the surface of the magnetic powder in two or more times from the surface treatment agent having a large occupied area of molecules when adsorbed on the surface of the magnetic powder as a magnetic material. Is.

Example 10 In Example 9, the magnetic coating material was prepared by using the magnetic powder which had been surface-treated three times in advance to prepare the magnetic recording medium. The magnetic powder of Comparative Example 1 and four kinds of surface treatment agents were sequentially added to the magnetic coating material in three times without surface treatment, and the surface treatment of the magnetic powder was performed to produce the magnetic powder. A magnetic coating material was prepared and coated on a non-magnetic support in the same manner as in Comparative Example 1 to prepare a magnetic recording medium. The magnetic powder and the magnetic recording medium are referred to as Example 10 for convenience.

The magnetic powder of Example 10 is to be surface-treated when a magnetic coating material having the composition shown in Comparative Example 1 is prepared using the magnetic powder of Comparative Example 1 which has not been surface-treated. However, in Example 10, 2 parts by weight of 1,8-naphthalic anhydride was added at the same time when the magnetic powder was added, and then one-third of the total kneading time passed during the preparation of the magnetic coating material. At that time, 2 parts by weight of phthalic anhydride was additionally charged, and when one third of the total kneading time had elapsed, 3 parts by weight of myristic acid and 1 part by weight of 12-hydroxylauric acid were additionally charged. As a result, 1,8-naphthalic anhydride, phthalic anhydride, myristic acid and 12-hydroxylauric acid were sequentially adsorbed on the surface of the magnetic powder during the kneading of the magnetic paint, and the surface treatment of the magnetic powder was performed. 10
Magnetic powder of Then, using the magnetic coating material containing the magnetic powder of Example 10, a magnetic tape was manufactured as a magnetic recording medium in the same manner as in Comparative Example 1.

Then, the magnetic characteristics, surface glossiness, and temporal stability of this magnetic recording medium were measured in the same manner as in Comparative Example 1. The results are also shown in Table 1.

As shown in the results of Table 1, this Example 1
It was confirmed that high magnetic dispersibility and high temporal stability (weather resistance) were ensured in the magnetic recording medium of No. 0 as in Example 9.

This is because when a magnetic coating material is prepared, a surface treatment agent having a large occupied area of molecules when adsorbed on the surface of the magnetic powder is sequentially added in two or more times, which is an excellent surface for the magnetic powder. It shows the processability.

From the results of Experimental Example 1 above, in the magnetic powder and the magnetic recording medium of the present invention, when the magnetic powder was subjected to surface treatment successively with two or more different surface treatment agents or their solutions, Among the surface treatment agents, the surface treatment agents are arranged in descending order of the area occupied by the molecules when these surface treatment agent molecules are adsorbed on the magnetic powder surface. After the first surface treatment agent having an occupied area is adsorbed on the magnetic powder, the first surface treatment agent is first adsorbed on the non-adsorbed part
The second surface-treating agent having a large occupied area is adsorbed next to the surface-treating agent of No. 1, and various surface treating agents are efficiently adhered to the surface of the magnetic powder, resulting in dispersibility and weather resistance. It was confirmed that the performance is improved.

That is, the magnetic recording medium of the present invention using the magnetic powder of the present invention as described above can sufficiently cope with high density recording.

<Experimental Example 2> In the present experimental example, in the magnetic powder obtained by sequentially performing surface treatment with two or more different surface treatment agents containing ω-hydroxycarboxylic acid, these surface treatment agents were used. Among them, the magnetic powder of the present invention and the magnetic recording of the present invention in which the surface treatment is performed in order from the surface treatment agent having the largest occupied area of the molecule when these surface treatment agent molecules are adsorbed on the surface of the magnetic powder. An example of the medium will be described. That is, the magnetic powder not subjected to the surface treatment and Comparative Example 1 which is a magnetic recording medium using the magnetic powder, and the surface treatments are performed in order from one having a large occupied area of two or more different surface treatment agents containing ω-hydroxycarboxylic acid. Manufactured magnetic powders and Examples 11 to 14 which are magnetic recording media using the magnetic powders were investigated, and the saturation magnetization of these magnetic powders, the magnetic properties and surface glossiness of these magnetic recording media, durability and stability over time were investigated. I decided. The manufacturing process of each magnetic powder and the magnetic recording medium and the experimental results are shown below together.

The above-mentioned magnetic properties, surface glossiness and stability over time shall be measured by the method described in Experimental Example 1. And the said durability was investigated by what is called a still test method. That is, the durability of the magnetic recording medium was measured by repeatedly scanning and reproducing the same portion of the magnetic recording medium with the magnetic head and deteriorating the quality of the reproduced image. At this time, the measured values of surface glossiness and durability were normalized with the measured value of Comparative Example 1 as 100%. Table 2
The measured values of each characteristic of Comparative Example 1 are shown in. In addition, Table 2 also shows measured values of respective characteristics of Examples 11 and 12 described later.

[0132]

[Table 2]

Example 11 In this example, the magnetic powder of Comparative Example 1 was coated with an organic compound from the state where the iron oxide layer was not present on the surface portion, that is, in the reduced state, to the magnetic powder subjected to the surface treatment. And naphthalic anhydride having a structure of C ₁₂ H ₆ O ₃ and CH ₃ (CH ₂ ) ₁₂ COOH as a surface treatment agent.
Magnetic powders sequentially subjected to surface treatment with myristic acid having the structure of were prepared, and using this magnetic powder, a magnetic recording medium was manufactured by the same method as in Comparative Example 1. The magnetic powder and the magnetic recording medium are referred to as Example 11 for convenience.

First, the raw material goethite α-FeOOH of the magnetic powder shown in Comparative Example 1 was gently filled in a reaction vessel, heated at 400 ° C. for 3 hours in a state of atmospheric flow, and dehydrated, and then hydrogenated. Switch to flow and continue as it is 400
Hydrogen reduction treatment was carried out at ℃ for 3 hours. After that, it is left to cool to near room temperature in a hydrogen flow state, then the hydrogen flow is stopped in a state where the reduced magnetic powder does not come into contact with the atmosphere, and subsequently methyl ether ((CH ₃ ) ₂ O) is injected into the reaction vessel. did. The sample obtained by the above operation was taken out of the reaction container, and the excess organic compound was dried in the atmosphere to obtain a magnetic powder. The saturation magnetization of this magnetic powder is shown in Table 2.

Next, 0.3 mol / l of naphthalic anhydride
A predetermined amount of the above magnetic powder was immersed in an ethanol solution, shaken in a vibration mill for 3 hours, and then only the magnetic powder was filtered, separated, and dried in the atmosphere. Furthermore, 0.2 of myristic acid
A predetermined amount of the above magnetic powder was immersed in a mol / l ethanol solution, shaken in a vibration mill for 3 hours, and then only the magnetic powder was filtered, separated, and dried in the atmosphere. That is, in this Example 11, the surface treatment was performed in order from the surface treatment agent having the largest occupied area of the surface treatment agent molecule when adsorbed on the surface of the magnetic powder.

Then, using this magnetic powder, a magnetic coating material was similarly prepared with the composition shown in Comparative Example 1, and a magnetic tape was manufactured as a magnetic recording medium in the same manner as in Comparative Example 1.

Then, the magnetic characteristics, surface glossiness and temporal stability of this magnetic recording medium were measured in the same manner as in Example 1,
The durability was also measured by the above method. The results are shown in Table 2.

As shown in the results of Table 2, this Example 1
The magnetic powder of No. 1 has high saturation magnetization, and the magnetic recording medium of Example 11 using the magnetic powder has high surface gloss, residual magnetic flux density and squareness ratio, and has a higher dispersion than that of Comparative Example 1. It is clear that sex has been obtained. In addition, Example 11
Also showed that the organic compound and the surface treatment agent, which were adsorbed on the surface of the magnetic powder in three times, provided excellent stability over time.

Further, it was confirmed that the magnetic recording medium of Example 11 had excellent durability.

This means that two kinds of surface treatment agents are added to the surface of the magnetic powder in addition to the magnetic powder surface-treated by depositing the organic compound from the reduced state where the iron oxide layer does not exist on the surface portion. The surface-treating agent exhibits excellent surface-treatability in that the surface-treating agent having a large occupied area of molecules when adsorbed on is sequentially deposited.

Example 12 In the above Example 11, magnetic powder surface-treated by applying an organic compound from the reduced state was further surface-treated with naphthalic anhydride and myristic acid. This is an example in which magnetic powder is obtained and a magnetic coating material is prepared by using the magnetic powder to prepare a magnetic recording medium. In this Example 12, the surface portion was not subjected to surface treatment with a surface treating agent in advance. Naphthalic anhydride and myristic acid were sequentially added to the magnetic paint when preparing the magnetic paint using the magnetic powder that had been surface-treated by applying an organic compound from the reduced state in which the iron oxide layer did not exist. In this example, the magnetic powder was added to the above to surface-treat the magnetic powder to obtain the magnetic powder, and the magnetic recording medium was produced using this. The magnetic powder and the magnetic recording medium are referred to as Example 12 for convenience.

First, in the same manner as in Example 11, the magnetic powder was surface-treated with an organic compound. However, tetrahydropyran (C ₅ H ₁₀ O) was used as the organic compound instead of methyl ether ((CH ₃ ) ₂ O). The values of the saturation magnetization of the magnetic powder thus obtained are shown in Table 2.

Next, a magnetic coating material having the composition shown in Comparative Example 1 was prepared using the magnetic powder thus obtained. However, in Example 12, as described above, 8 parts by weight of naphthalic anhydride was added at the same time as the addition of the magnetic powder, and 6 parts by weight of myristic acid was additionally added when half the total kneading time had elapsed. This allows naphthalic anhydride and myristic acid to be sequentially deposited on the surface of the magnetic powder when the magnetic paint is kneaded.
The magnetic powder is adsorbed, and the surface treatment of the magnetic powder is carried out to obtain the magnetic powder of Example 12. Then, using the magnetic coating material containing the magnetic powder of Example 12, a magnetic tape was manufactured as a magnetic recording medium in the same manner as in Comparative Example 1.

Then, the magnetic characteristics, surface glossiness, temporal stability and durability of this magnetic recording medium were measured in the same manner as in Example 11. The results are shown in Table 2.

As shown in the results of Table 2, this Example 1
It was confirmed that the magnetic powder of No. 2 also has a high saturation magnetization, and the magnetic recording medium of the present Example 12 using this also has high dispersibility and stability over time.

Further, it was confirmed that the magnetic recording medium of Example 12 also had excellent durability.

This is because the magnetic powder which has been surface-treated by depositing an organic compound from the reduced state, and the molecules when two types of surface-treating agents were adsorbed on the surface of the magnetic powder during preparation of the magnetic paint. The surface-treating agent exhibits excellent surface-treatability by sequentially adding the surface-treating agent having a large occupation area.

From the results of Experimental Example 2 above, in the magnetic powder and the magnetic recording medium of the present invention, various surface treatment agents were efficiently applied to the magnetic powder, and as a result, the dispersibility and weather resistance were good. It was confirmed that

Further, in the present experimental example, one of two or more different surface treatment agents was ω-hydroxycarboxylic acid, and the carboxyl group in these carboxylic acids was adsorbed on the surface of the magnetic powder to give the magnetic powder. It is considered that the active points on the surface lose their activity and the weather resistance of the magnetic powder is improved.

Furthermore, in the present experimental example, ω-hydroxycarboxylic acid was used as the surface treatment agent, and this was used as the magnetic paint, and the magnetic chain was changed by the affinity between the alkyl chain in the carboxylic acid and the binder or the organic solvent. The powder obtained a high dispersibility in the binder, which is also considered to improve the magnetic properties and the surface gloss.

From the results of Experimental Example 2, when the magnetic powder was prepared by previously depositing an organic compound on the reduced magnetic powder, high magnetization of the magnetic powder was ensured and stability with time was improved. It was also confirmed to be good.

That is, the magnetic recording medium of the present invention using the magnetic powder of the present invention as described above can sufficiently cope with high density recording.

<Experimental Example 3> In this Experimental Example, magnetic properties obtained by sequentially performing surface treatment with two or more different surface treatment agents containing a linear carboxylic acid having an unsaturated bond at the ω-position or solutions thereof. In the powder, among these surface treatment agents, the magnetic powder of the present invention and the magnetic powder of the present invention, which are subjected to surface treatment in order from the surface treatment agent having a large occupied area of the molecule when these surface treatment agent molecules are adsorbed on the surface of the magnetic powder. An example of the magnetic recording medium used will be described. That is, the occupying area of two or more different surface treatment agents containing a magnetic powder not subjected to surface treatment and Comparative Examples 1 and 4 which are magnetic recording media using the same and a linear carboxylic acid having an unsaturated bond at the ω-position are Magnetic powders subjected to surface treatment in order from the largest one and Examples 13 to 18, which are magnetic recording media using the same, were manufactured, and the saturation magnetization of these magnetic powders, the magnetic properties and surface glossiness of these magnetic recording media, and durability. It was decided to investigate the sex and stability over time. The manufacturing process of each magnetic powder and the magnetic recording medium and the experimental results are shown below together.

Comparative Example 4 Here, a commercially available needle-shaped metallic iron magnetic powder for magnetic recording (specific surface area 53.9 m ² / g, coercive force Hc = 126.5 kA /
m, saturation magnetization σs = 120 Am ² / kg, average major axis length 0.3 μm, acicular ratio 8 to 10), and a magnetic recording medium was produced. Note that this magnetic powder and the magnetic recording medium will be referred to as Comparative Example 4 for convenience.

That is, a magnetic coating material having the following composition was prepared, coated on a polyester base film having a thickness of 30 μm, oriented with an orientation magnetic field of 5000 gauss, and then dried at 60 ° C. for 5 minutes. Acceleration voltage 150
A magnetic tape was produced as a magnetic recording medium by irradiating with an electron beam of keV.

Needle-shaped metallic iron magnetic powder for magnetic recording 100 parts by weight Electron beam curable vinyl chloride-vinyl acetate copolymer having an acrylic double bond 10 parts by weight Electron beam curable polyurethane resin having an acrylic double bond 10 Parts by weight Carbon 3 parts by weight Aluminum oxide 2 parts by weight Methyl ethyl ketone 100 parts by weight Toluene 100 parts by weight Cyclohexanone 50 parts by weight Experimental examples of magnetic properties, surface gloss, temporal stability and durability of the magnetic recording medium thus obtained 1 and Experimental Example 2
It was measured by the method described above. Regarding the measured values of surface glossiness and durability, the measured value of Comparative Example 1 was 10
Normalized as 0%. Table 3 shows the above measured values in Comparative Example 1 and Comparative Example 4. In addition, Example 13 to be described later.
The results of 18 are also shown in Table 3.

[0157]

[Table 3]

Example 13 In this example, the magnetic powder of Comparative Example 1 was coated with an organic compound from the reduced state where the iron oxide layer was not present on the surface portion, and 4-having a structure of C ₁₂ H ₅ NO ₅ as a surface treatment agent
Nitro - naphthalic anhydride and C ₈ H ₃ having the structure of NO ₅ 3- nitro - phthalic anhydride with CH ₃ (CH _{2) 12} CO
Magnetic powders sequentially subjected to surface treatment with myristic acid having an OH structure were prepared, and the magnetic powders were used to fabricate a magnetic recording medium by the same method as in Comparative Example 1. In addition,
The above magnetic powder and magnetic recording medium are referred to as Example 13 for convenience.

First, the raw material goethite α-FeOOH of the magnetic powder shown in Comparative Example 1 was gently charged into a reaction vessel, heated at 400 ° C. for 3 hours in a state of atmospheric flow, and dehydrated. Switch to flow and continue as it is 400
Hydrogen reduction treatment was carried out at ℃ for 3 hours. After that, the mixture was left to cool to near room temperature in a hydrogen flow state, then the hydrogen flow was stopped in a state where the reduced magnetic powder did not come into contact with the atmosphere, and subsequently tetrahydrofuran (C ₄ H ₈ O) was injected into the reaction vessel. The sample obtained by the above operation was taken out of the reaction container, and the excess organic compound was dried in the atmosphere to obtain a magnetic powder. The saturation magnetization of this magnetic powder is shown in Table 3.

Then, 4-nitro-naphthalic anhydride of 0.
A predetermined amount of the magnetic powder was immersed in a 3 mol / l ethanol solution, shaken in a vibration mill for 3 hours, and then only the magnetic powder was filtered, separated, and dried in the atmosphere. Then, a predetermined amount of the above magnetic powder was immersed in a 0.2 mol / l ethanol solution of 3-nitro-phthalic anhydride, shaken in a vibration mill for 3 hours, and then only the magnetic powder was filtered, separated and dried in the atmosphere. did. Further, a predetermined amount of the magnetic powder was immersed in a 0.3 mol / l ethanolic solution of myristic acid, shaken in a vibration mill for 3 hours, and then only the magnetic powder was filtered, separated and dried in the atmosphere. That is, in this Example 13, the surface treatment was carried out in order from the surface treatment agent having the largest occupied area of the surface treatment agent molecule when adsorbed on the surface of the magnetic powder.

Then, using this magnetic powder, a magnetic coating material was similarly prepared with the composition shown in Comparative Example 1, and a magnetic tape was manufactured as a magnetic recording medium in the same manner as in Comparative Example 1.

Then, the magnetic properties, surface glossiness, temporal stability and durability of this magnetic recording medium were measured in the same manner as in Experimental Examples 1 and 2. The results are shown in Table 3.

As shown in the results of Table 3, this Example 1
The magnetic powder of No. 3 has high saturation magnetization, and the magnetic recording medium of Example 13 using the same has high surface gloss, residual magnetic flux density, and squareness ratio, and has a higher dispersion than that of Comparative Example 1. It is clear that sex has been obtained. In addition, Example 13
Also showed that the organic compound and the surface treatment agent, which were adsorbed on the surface of the magnetic powder in three times, provided excellent stability over time.

Further, it was confirmed that the magnetic recording medium of Example 13 had excellent durability.

This is because the occupied area of molecules when three kinds of surface treatment agents are adsorbed on the surface of the magnetic powder with respect to the magnetic powder surface-treated by depositing an organic compound from the reduced state. The surface-treating agent having a large surface treatment property is successively coated to exhibit excellent surface-treating property.

Example 14 In the above-mentioned Example 13, 4-nitro-naphthalic anhydride and 3-nitro-phthalic anhydride were added to the magnetic powder surface-treated by applying an organic compound from the reduced state. This is an example of preparing a magnetic recording medium by using a magnetic powder that has been sequentially surface-treated with and a myristic acid to prepare a magnetic recording medium. In this Example 14, the surface treatment of the magnetic powder with a surface-treating agent was performed in advance. Without preparing, 4-nitro-naphthalic anhydride and 4-nitro-naphthalic anhydride were used when preparing a magnetic coating using a magnetic powder surface-treated by depositing an organic compound from the reduced state where the iron oxide layer does not exist on the surface. 3-nitro-phthalic anhydride and myristic acid sequentially,
This is an example in which a magnetic powder is obtained by adding it to a magnetic paint and a magnetic recording medium is produced using this. The magnetic powder and magnetic recording medium are referred to as Example 14 for convenience.

First, the magnetic powder was surface-treated with an organic compound in the same manner as in Example 13. The values of the saturation magnetization of the magnetic powder thus obtained are shown in Table 3.

Next, a magnetic coating material having the composition shown in Comparative Example 1 was prepared using the magnetic powder thus obtained. However, in Example 14, as described above, 8 parts by weight of 4-nitro-naphthalic anhydride was added at the same time when the magnetic powder was charged, and further, when 1/3 of the total kneading time had elapsed, 3
An additional 6 parts by weight of -nitro-phthalic anhydride was added, and when 2/3 of the total kneading time had elapsed, an additional 8 parts by weight of myristic acid was added. As a result, 4-nitro-naphthalic anhydride, 3-nitro-phthalic anhydride, and myristic acid were sequentially adsorbed on the surface of the magnetic powder during the kneading of the magnetic paint, and the surface treatment of the magnetic powder was performed. A magnetic powder is obtained. Then, using the magnetic coating material containing the magnetic powder of Example 14, a magnetic tape was manufactured as a magnetic recording medium in the same manner as in Comparative Example 1.

Then, the magnetic characteristics, surface glossiness, aging stability and durability of this magnetic recording medium were measured in the same manner as in Example 11. The results are shown in Table 3.

As shown in the results of Table 3, this Example 1
It was confirmed that the magnetic powder of No. 4 also has a high saturation magnetization, and the magnetic recording medium of this Example 14 using this also has high dispersibility and stability over time.

Further, it was confirmed that the magnetic recording medium of Example 14 also had excellent durability.

This means that when the magnetic powder was surface-treated by depositing an organic compound from the reduced state, three kinds of surface-treating agents were adsorbed on the surface of the magnetic powder during preparation of the magnetic paint. The surface-treating agent exhibits excellent surface-treatability by sequentially adding the surface-treating agent having a large occupation area.

Example 15 In this example, a magnetic powder surface-treated by depositing an organic compound on the magnetic powder of Comparative Example 1 from the state where no iron oxide layer was present on the surface portion, that is, the reduced state was used. As a surface treatment agent, naphthalic anhydride having a structure of C ₁₂ H ₆ O ₃ , then phthalic anhydride having a structure of C ₈ H ₄ O ₃ , and then CH ₃ (CH ₂ ) ₁₄ COO.
Palmitic acid having the structure of H and CH ₂ = CH (CH
₂ ) A magnetic powder was prepared by sequentially surface-treating it with a mixture of 22-tricosenoic acid having a structure of ₂₀ COOH, and using this magnetic powder, a magnetic recording medium was produced in the same manner as in Comparative Example 4. The magnetic powder and the magnetic recording medium are referred to as Example 15 for convenience.

First, the magnetic powder was surface-treated with an organic compound in the same manner as in Example 13. The saturation magnetization of this magnetic powder is shown in Table 3.

Next, 0.3 mol / l of naphthalic anhydride
A predetermined amount of the above magnetic powder was immersed in an ethanol solution, shaken in a vibration mill for 3 hours, and then only the magnetic powder was filtered, separated, and dried in the atmosphere. Then 0.2 of phthalic anhydride
A predetermined amount of the above magnetic powder was immersed in a mol / l ethanol solution, shaken in a vibration mill for 3 hours, and then only the magnetic powder was filtered, separated, and dried in the atmosphere. Further, a predetermined amount of the above magnetic powder was immersed in a mixed solution of a 0.2 mol / l ethanolic solution of palmitic acid and a 0.1 mol / l ethanolic solution of 22-tricosenoic acid, and the magnetic powder was shaken in a vibration mill for 3 hours. Only the product was filtered, separated and dried in the atmosphere. That is, in this Example 15, the surface treatment was performed in order from the surface treatment agent having the largest occupied area of the surface treatment agent molecule when adsorbed on the surface of the magnetic powder.

Then, using this magnetic powder, a magnetic coating material was similarly prepared with the composition shown in Comparative Example 4, and a magnetic tape was manufactured as a magnetic recording medium in the same manner as in Comparative Example 4.

Then, the magnetic characteristics, surface glossiness, temporal stability and durability of this magnetic recording medium were measured in the same manner as in Example 13. The results are shown in Table 3.

As shown in the results of Table 3, this Example 1
The magnetic powder of No. 5 has high saturation magnetization, and the magnetic recording medium of Example 15 using the same has high surface gloss, residual magnetic flux density, and squareness ratio, and has a higher dispersion than Comparative Example 4. It is clear that sex has been obtained. In addition, Example 15
Also showed that the organic compound adsorbed on the surface of the magnetic powder gives excellent stability over time.

Further, the magnetic recording medium of the present Example 15 also has good durability, because the unsaturated bond in the binder molecule and the undecylenic acid in the binder molecule are affected by the electron beam irradiated for curing. It is considered that the saturated bonds were cross-linked with each other.

This means that four kinds of surface treatment agents were added to the surface of the magnetic powder in addition to the magnetic powder surface-treated by depositing an organic compound from the reduced state where the iron oxide layer did not exist on the surface portion. The surface-treating agent exhibits excellent surface-treatability in that the surface-treating agent having a large occupied area of molecules when adsorbed on is sequentially deposited.

Example 16 In Example 15, the magnetic powder surface-treated by applying an organic compound from the reduced state was further mixed with naphthalic anhydride, phthalic anhydride and palmitic acid. This is an example of preparing a magnetic recording medium by preparing a magnetic coating material by using magnetic powders which are sequentially surface-treated with a mixture with tricosenoic acid.
Is a magnetic coating material that uses a magnetic powder that has been surface-treated by depositing an organic compound from the reduced state in which the iron oxide layer does not exist on the surface portion, without performing surface treatment on the magnetic powder in advance. In the preparation of naphthalic anhydride, then phthalic anhydride, and then a mixture of palmitic acid and 22-tricosenoic acid are sequentially added to the magnetic paint to perform surface treatment of the magnetic powder to obtain magnetic powder. This is an example of producing a magnetic recording medium by using. The magnetic powder and the magnetic recording medium are referred to as Example 16 for convenience.

First, in the same manner as in Example 15, the magnetic powder was surface-treated with an organic compound. The values of the saturation magnetization of the magnetic powder thus obtained are shown in Table 3.

Next, using the magnetic powder thus obtained, a magnetic coating material was prepared with the composition shown in Comparative Example 4. However, in Example 16, as described above, 8 parts by weight of naphthalic anhydride was added at the same time as the addition of the magnetic powder, and 6 parts by weight of phthalic anhydride was added at the time when 1/3 of the total kneading time had elapsed. Additional addition, and when two-thirds of the total kneading time had elapsed, 6 parts by weight of palmitic acid and 3 parts by weight of 22-tricosenoic acid were additionally added. As a result, naphthalic anhydride and phthalic anhydride, palmitic acid and 22-tricosenoic acid were sequentially adsorbed on the surface of the magnetic powder during the kneading of the magnetic paint, and the surface treatment of the magnetic powder was performed. can get. Then, using the magnetic coating material containing the magnetic powder of Example 16, a magnetic tape was manufactured as a magnetic recording medium in the same manner as in Comparative Example 4.

Then, the magnetic characteristics, surface glossiness, temporal stability and durability of this magnetic recording medium were measured in the same manner as in Example 13. The results are shown in Table 3.

As shown in the results of Table 3, this Example 1
It was confirmed that the magnetic powder of No. 6 also has a high saturation magnetization, and that the magnetic recording medium of the present Example 16 using this also has high dispersibility, stability over time, and durability.

This means that four kinds of surface treatment agents were added to the magnetic powder during the preparation of the magnetic coating material, together with the magnetic powder surface-treated by depositing the organic compound on the surface portion in the state where the iron oxide layer was not present. It shows excellent surface treatment property when sequentially added from the surface treatment agent having a large occupied area of molecules when adsorbed on the powder surface.

Example 17 In this example, the magnetic powder of Comparative Example 1 was coated with an organic compound from the state where the iron oxide layer was not present on the surface portion, that is, in the reduced state, to the magnetic powder subjected to the surface treatment. 4-amino-naphthalic anhydride having a structure of C ₁₂ H ₇ NO ₃ as a surface treatment agent, and then CH ₃
Capric acid having the structure of (CH ₂ ) ₈ COOH and CH
₂ = CH (CH ₂ ) ₈ COOH A magnetic powder which was sequentially surface-treated with a mixture with undecylenic acid having a structure was prepared, and this magnetic powder was used to prepare a magnetic recording medium in the same manner as in Comparative Example 4. It was made. The magnetic powder and the magnetic recording medium are referred to as Example 17 for convenience.

First, the magnetic powder was surface-treated with an organic compound in the same manner as in Example 13. However, methyl ether ((CH ₃ ) ₂ O) was used instead of tetrahydrofuran (C ₄ H ₈ O). The values of the saturation magnetization of the magnetic powder thus obtained are shown in Table 3.

Then, 4-amino-naphthalic anhydride of 0.
A predetermined amount of the magnetic powder was immersed in a 3 mol / l ethanol solution, shaken in a vibration mill for 3 hours, and then only the magnetic powder was filtered, separated, and dried in the atmosphere. Further, a predetermined amount of the magnetic powder was immersed in a mixed solution of a 0.2 mol / l ethanol solution of capric acid and a 0.1 mol / l ethanol solution of undecylenic acid, and after shaking for 3 hours in a vibration mill, only the magnetic powder was removed. It was filtered, separated and dried in air. That is, in this Example 17, the surface treatment was performed in order from the surface treatment agent having the largest occupied area of the surface treatment agent molecule when adsorbed on the surface of the magnetic powder.

Then, using this magnetic powder, a magnetic coating material was similarly prepared with the composition shown in Comparative Example 4, and a magnetic tape was manufactured as a magnetic recording medium in the same manner as in Comparative Example 4.

Then, the magnetic characteristics, surface glossiness, temporal stability and durability of this magnetic recording medium were measured in the same manner as in Example 13. The results are shown in Table 3.

As shown in the results of Table 3, this Example 1
The magnetic powder of Example 7 has a high saturation magnetization, and the magnetic recording medium of Example 17 using the same has a high surface gloss, a residual magnetic flux density, and a squareness ratio, and has a higher dispersion than that of Comparative Example 4. It is clear that sex has been obtained. In addition, Example 17
Also showed that the organic compound adsorbed on the surface of the magnetic powder gives excellent stability over time.

Furthermore, the magnetic recording medium of this Example 17 also had good durability, which was due to the unsaturated bond in the binder molecule and the undecylenic acid in the binder molecule due to the electron beam irradiated for curing. It is considered that the saturated bonds were cross-linked with each other.

This means that the area occupied by molecules when three types of surface treatment agents are adsorbed on the surface of the magnetic powder with respect to the magnetic powder surface-treated by depositing an organic compound from the reduced state. The surface-treating agent having a large surface treatment property is successively coated to exhibit excellent surface-treating property.

Example 18 In the above Example 17, magnetic powder surface-treated by depositing an organic compound from the reduced state was further treated with 4-amino-naphthalic anhydride, followed by capric acid and undecylenic acid. In this example, a magnetic recording medium is prepared by preparing a magnetic coating material by using magnetic powder which is sequentially surface-treated with the mixture of Example 1. In Example 18, the magnetic powder is surface-treated with a surface-treating agent in advance. 4-amino-naphthalic anhydride when preparing a magnetic coating material using a magnetic powder surface-treated by depositing an organic compound from a reduced state in which the iron oxide layer does not exist on the surface portion, A mixture of capric acid and undecylenic acid was sequentially added to the magnetic paint to surface-treat the magnetic powder to obtain magnetic powder. An example of manufacturing the recording medium. The magnetic powder and magnetic recording medium are referred to as Example 18 for convenience.

First, the magnetic powder was surface-treated with an organic compound in the same manner as in Example 13. However, tetrahydropyran (C ₅ H ₁₀ O) was used instead of tetrahydrofuran (C ₄ H ₈ O). The values of the saturation magnetization of the magnetic powder thus obtained are shown in Table 3.

Next, a magnetic coating material having the composition shown in Comparative Example 4 was prepared using the magnetic powder thus obtained. However, in Example 18, as described above, 8 parts by weight of 4-amino-naphthalic anhydride was added at the same time as the addition of the magnetic powder, and further 6 parts by weight of capric acid was added when half the total kneading time had elapsed. Undecylenic acid and 3 parts by weight were additionally added. As a result, 4-amino-naphthalic anhydride, capric acid, and undecylenic acid were sequentially adsorbed on the surface of the magnetic powder during the kneading of the magnetic coating material, and the surface treatment of the magnetic powder was performed to obtain the magnetic powder of Example 18. . Then, using the magnetic coating material containing the magnetic powder of Example 18, a magnetic tape was manufactured as a magnetic recording medium in the same manner as in Comparative Example 4.

Then, the magnetic properties, surface glossiness, temporal stability and durability of this magnetic recording medium were measured in the same manner as in Example 13. The results are shown in Table 3.

As shown in the results of Table 3, this Example 1
It was confirmed that the magnetic powder of Example 8 also has high saturation magnetization, and that the magnetic recording medium of Example 18 using the same also ensures high dispersibility, stability over time, and durability.

This means that, together with the magnetic powder surface-treated by depositing an organic compound from the reduced state, the molecules when three kinds of surface-treating agents were adsorbed on the surface of the magnetic powder during the preparation of the magnetic paint. The surface-treating agent exhibits excellent surface-treatability by sequentially adding the surface-treating agent having a large occupation area.

From the results of Experimental Example 3 above, in the magnetic powder and the magnetic recording medium of the present invention, various surface treatment agents were efficiently applied to the magnetic powder, and as a result, the dispersibility and weather resistance were good. It was confirmed that

In this experimental example, one of two or more different surface treatment agents was a straight chain carboxylic acid having an unsaturated bond at the ω-position, and the carboxyl group in these carboxylic acids was a magnetic powder. It is considered that the active points on the surface of the magnetic powder lose their activity after being adsorbed on the surface and the weather resistance of the magnetic powder is improved.

Furthermore, in this experimental example, a linear carboxylic acid having an unsaturated bond at the ω-position was used as a surface treatment agent, and this was used as a magnetic paint, and the alkyl chain in the carboxylic acid and the binder or organic compound were used. It is considered that the magnetic powder has a high dispersibility in the binder due to the affinity with the solvent, and this also improves the magnetic properties and the surface gloss.

From the results of Experimental Example 3, if the magnetic powder is a magnetic powder in a reduced state and an organic compound is pre-deposited on the magnetic powder, a high magnetization of the magnetic powder is ensured and stability over time is improved. It was also confirmed to be good.

That is, the magnetic recording medium of the present invention using the magnetic powder of the present invention as described above can sufficiently cope with high density recording.

[0206]

As is apparent from the above description, in the magnetic powder and the magnetic recording medium of the present invention, the magnetic powder is sequentially surface-treated with two or more different surface treating agents or their solutions. Of these surface treatment agents, since the surface treatment agents having a large occupied area of the molecule when these surface treatment agent molecules are adsorbed on the surface of the magnetic powder are sequentially subjected to the surface treatment, After adsorbing the first surface compound having the largest occupied area of these surface treatment agents on the magnetic powder, a large occupied area subsequent to the first surface treatment agent on the non-adsorbed portion of the first surface treatment agent. To adsorb the second surface treatment agent having
This means that various surface treatment agents are effectively deposited on the surface of the magnetic powder. Therefore, in the magnetic powder and the magnetic recording medium of the present invention, the dispersibility and weather resistance can be effectively improved by selecting the type of the surface treatment agent for the magnetic powder.

At this time, if the magnetic powder is formed by previously depositing an organic compound on the reduced magnetic powder, a high magnetization of the magnetic powder is secured and the temporal stability is further improved.

In the magnetic powder and the magnetic recording medium of the present invention, one of the two or more different surface treatment agents may be ω-hydroxycarboxylic acid or a linear carboxylic acid having an unsaturated bond at the ω position. For example, the carboxyl groups in these carboxylic acids are adsorbed on the surface of the magnetic powder and the active sites on the surface of the magnetic powder lose their activity, so the weather resistance of the magnetic powder is improved.

Further, when the above-mentioned surface treatment agent is used, when the magnetic powder of the present invention is used as a magnetic coating material, the magnetic powder is formed by the affinity between the alkyl chain in the carboxylic acid and the binder or the organic solvent. A high dispersibility in the binder is obtained, and the dispersibility of the magnetic powder in the magnetic layer of the magnetic recording medium of the present invention is good.

That is, the magnetic recording medium of the present invention using the magnetic powder of the present invention as described above can sufficiently cope with high density recording.

Claims (20)

[Claims] 1. A magnetic powder, which is sequentially surface-treated with two or more different surface-treating agents or solutions thereof, wherein molecules of the surface-treating agent of these surface-treating agents are adsorbed on the surface of the magnetic powder. A magnetic powder characterized by being subjected to surface treatment in order from a surface treatment agent having a large occupied area of molecules at that time. 2. The magnetic powder according to claim 1, wherein the magnetic powder is obtained by previously depositing an organic compound on the reduced magnetic powder. 3. The magnetic powder according to claim 1, wherein one of the two or more different surface treatment agents is ω-hydroxycarboxylic acid. 4. The occupied area of a surface treatment agent molecule other than ω-hydroxycarboxylic acid among two or more different surface treatment agents adsorbed on the surface of the magnetic powder is such that the ω-hydroxycarboxylic acid molecule is the surface of the magnetic powder. The magnetic powder according to claim 3, wherein the magnetic powder has a larger area than when it is adsorbed on. 5. The magnetic powder according to claim 3, wherein the magnetic powder is obtained by previously depositing an organic compound on the reduced magnetic powder. 6. The magnetic powder according to claim 4, wherein the magnetic powder is obtained by previously depositing an organic compound on the reduced magnetic powder. 7. The magnetic powder according to claim 1, wherein one of the two or more different surface treatment agents is a linear carboxylic acid having an unsaturated bond at the ω position. 8. An occupied area when a surface-treating agent molecule other than a linear carboxylic acid having an unsaturated bond at the ω-position among two or more different surface-treating agents is adsorbed on the surface of the magnetic powder,
The magnetic powder according to claim 7, wherein the linear carboxylic acid molecule having an unsaturated bond at the ω-position is larger than the occupied area when adsorbed on the surface of the magnetic powder. 9. The magnetic powder according to claim 7, wherein the magnetic powder is obtained by previously depositing an organic compound on the reduced magnetic powder. 10. The magnetic powder according to claim 8, wherein the magnetic powder is obtained by previously depositing an organic compound on the reduced magnetic powder. 11. A magnetic recording medium comprising a magnetic layer mainly composed of a magnetic powder and a binder formed on a non-magnetic support, wherein the magnetic powder comprises two or more different surface treatment agents or solutions thereof. The surface treatment agent is subjected to surface treatment in order from the surface treatment agent having the largest area occupied by the molecules when these surface treatment agent molecules are adsorbed on the magnetic powder surface. A magnetic recording medium characterized in that 12. The magnetic recording medium according to claim 11, wherein the magnetic powder is obtained by previously depositing an organic compound on the reduced magnetic powder. 13. The magnetic recording medium according to claim 11, wherein one of the two or more different surface treatment agents is ω-hydroxycarboxylic acid. 14. The occupied area of a surface treatment agent molecule other than ω-hydroxycarboxylic acid among two or more different surface treatment agents adsorbed on the surface of the magnetic powder is such that the ω-hydroxycarboxylic acid molecule is the surface of the magnetic powder. 14. The magnetic recording medium according to claim 13, wherein the magnetic recording medium has a larger area than the area occupied by the magnetic recording medium. 15. The magnetic recording medium according to claim 13, wherein the magnetic powder is obtained by previously depositing an organic compound on the reduced magnetic powder. 16. The magnetic recording medium according to claim 14, wherein the magnetic powder is obtained by previously depositing an organic compound on the reduced magnetic powder. 17. The magnetic recording medium according to claim 11, wherein one of the two or more different surface treatment agents is a linear carboxylic acid having an unsaturated bond at the ω position. 18. The occupied area of a surface-treating agent molecule other than a linear carboxylic acid having an unsaturated bond at the ω-position among two or more different surface-treating agents is adsorbed on the surface of the magnetic powder at the ω-position. 18. The magnetic recording medium according to claim 17, wherein the linear carboxylic acid molecule having an unsaturated bond has a larger area than the occupied area when adsorbed on the surface of the magnetic powder. 19. The magnetic recording medium according to claim 17, wherein the magnetic powder is obtained by previously depositing an organic compound on the reduced magnetic powder. 20. The magnetic recording medium according to claim 18, wherein the magnetic powder is obtained by previously depositing an organic compound on the reduced magnetic powder.