JP3456102B2 - Magnetic particle powder, method for producing the same, and magnetic recording medium using the magnetic particle powder - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to excellent dispersibility and oxidation stability regardless of whether the polar group of the binder resin used in the coating type magnetic recording medium is an acidic group or a basic group. The present invention relates to a magnetic particle powder that is excellent in magnetic properties and is less likely to deteriorate with time, a method for producing the same, and a magnetic recording medium using the magnetic particle powder.

[0002]

2. Description of the Related Art In recent years, finer iron oxide magnetic particle powders, and further metal magnetic particle powders containing iron as a main component having higher magnetic characteristics have been used due to the demand for high density recording.

However, fine iron oxide magnetic particle powder and metallic magnetic particle powder containing iron as a main component tend to have poor wettability with the binder resin as the surface area of the particle powder increases. Therefore, in recent years, most of the binder resins used in coating type magnetic recording media have an acidic polar group or a basic polar group in order to improve compatibility with the magnetic powder. In that case, for example, when the surface of the particles of the magnetic powder is modified by surface treatment or the like in order to improve compatibility with the resin having an acidic polar group, the resin having an acidic polar group is more compatible, but is basic. There was a problem that the resin having the polar group of (3) gelled and was not dispersed at all.

Therefore, there is a demand for magnetic particle powders exhibiting sufficient dispersibility regardless of whether the binder resin used in the coating type magnetic recording medium has an acidic group or a basic group as a polar group.

Further, the metal magnetic particle powder containing iron as a main component is described in "Development of Magnetic Material and High Dispersion Technology of Magnetic Powder" (Published by Sogo Gijutsu Center Co., Ltd., 1982) No. 54
"There were some technical difficulties in putting metal powder to practical use. One of them was how to solve the protection against rust. Gamma iron oxide, chromium dioxide, Cobalt-coated iron oxide etc. are all
"Oxide". Oxide is a state in which oxygen ions have already formed ionic bonds with metal ions and are incorporated into the crystal lattice. On the other hand, metal powders are basically different. It is metal powders whose main constituents are iron atoms that you want to associate with oxygen.Oxygen and moisture in the air help to avoid rusting iron, so you don't miss any small crystal gaps. Therefore, it is necessary to devise a metal powder that is more than enough for oxidation resistance, and how to express it in a way that allows the metal powder to settle in the coating film of the tape so that rust does not occur. It can be said that this is the most technically difficult point. "
Since it is easily oxidized in air, the magnetic recording medium using the metal magnetic particle powder containing iron as a main component is oxidized in the metal magnetic particle powder containing iron as a main component during storage, resulting in deterioration of magnetic characteristics. There were cases where problems such as doing occurred. Oxidation stability tends to be further deteriorated due to the increase in specific surface area associated with the recent finer particles. Conventionally, attempts have been made to improve the oxidative stability by forming an oxide film on the particle surface of the metal magnetic particle powder containing iron as a main component, but a sufficient one has not been obtained yet.

Therefore, there has been a demand for a magnetic metal particle powder containing iron as a main component, which is further excellent in oxidation stability.

Conventionally, various substances have been tried as surface treatment agents for improving oxidative stability. For example, ferromagnetic metal fine particles whose surface is treated with 3,4-dihydroxy-3-cyclobutene-1,2-dione (square acid), which is a 4-membered ring compound, and a magnetic recording medium using the same (US Pat. 225552), ferromagnetic metal fine particles whose surface is treated with an aromatic organic acid having an anthraquinone skeleton (such as alizarin), and a magnetic recording medium using the same (JP-A-5-225553).

Aluminum chelate compounds have been used for surface modification of pigments and magnetic powders. For example, a method of blending an aluminum chelate compound as a curing agent into a paint immediately before coating (Japanese Patent Publication No. 4-65873). (Japanese Patent Publication No. 61-26830) and the like, and a surface modifier for a powdery granular material containing at least one aluminum chelate compound having a specific structure and having a hydrophilic surface.

A magnetic recording medium using an aluminum chelate compound as a magnetic powder is a magnetic recording medium using a ferromagnetic powder surface-treated with an organic aluminum compound (JP-A-57-60535), Radiation-curable magnetic coating composition containing a magnetic pigment surface-treated with a specific aluminum-based metal coordination compound (Japanese Patent Publication No. 6-4786).
Issue gazette).

[0010]

The binder resin used in a magnetic recording medium has excellent dispersibility regardless of whether the polar group of the binder resin has an acidic group or a basic group, and is excellent in oxidation stability. A magnetic particle powder with little deterioration with time has not been obtained.

That is, in the case of the metal magnetic particle powder having only the coating layer of squaric acid described in JP-A-5-225552, and the coating layer of anthraquinone skeleton polyol described in JP-A-5-225553. In the case of a single-layer coating of metallic magnetic particle powder having only the above, as shown in Comparative Examples 2 and 3 below, sufficient dispersibility of either an acidic group or a basic group with respect to a resin having a polar group is obtained. I don't have it.

The pigment particles having a coating layer made of an aluminum chelate compound described in JP-B-61-26830 and JP-A-4-65873 have a role as a curing agent or a hydrophilic property as a function of the aluminum chelate compound. It has a role of changing the surface of the material to lipophilicity.

In the case of the magnetic particle powder consisting of the magnetic particles having the aluminum chelate compound single layer coating described in JP-A-57-60535 and JP-B-6-4786, it is easy to come off when made into a magnetic paint. However, it does not sufficiently contribute to improving the dispersibility of the magnetic particle powder in the binder resin.

Therefore, in the present invention, the binder resin has good dispersibility regardless of whether the polar group of the binder resin is an acidic group or a basic group and is excellent in oxidative stability, so that the magnetic properties are not deteriorated with time. A technical problem is to provide a small amount of magnetic particle powder.

[0015]

The above technical problems can be achieved by the present invention as follows.

That is, a magnetic particle having a coating layer composed of two layers, a lower layer and an upper layer, on the surface of the particle, wherein the lower layer is a coating layer made of squaric acid, and the upper layer is aluminum represented by the following general formula 11. Magnetic particle powder consisting of magnetic particles, which is a coating layer made of one or more aluminum chelate compounds selected from chelate compounds,

[Chemical 11]

A magnetic particle having a coating layer composed of two layers, a lower layer and an upper layer, on the surface of the particle, wherein the lower layer is a coating layer made of an anthraquinone skeleton polyol represented by the following general formula 12.

[Chemical 12] Magnetic particle powder composed of magnetic particles, wherein the upper layer is a coating layer composed of one or more aluminum chelate compounds selected from the aluminum chelate compounds represented by the general formula,

A magnetic particle having a coating layer consisting of a lower layer and an upper layer on the surface of the particle, wherein the lower layer is a coating layer comprising squaric acid and an anthraquinone skeleton polyol represented by the general formula, and the upper layer is One or two selected from aluminum chelate compounds represented by the general formula
Magnetic particle powder consisting of magnetic particles, which is a coating layer made of one or more aluminum chelate compounds,

The first step of forming a coating layer of squaric acid on the particle surface of the magnetic particles by mixing the magnetic particle powder and squaric acid in water or alcohol as a medium, then filtering and drying. The magnetic particle powder having a coating layer made of squaric acid formed on the surface of the particles through the steps and one or more kinds selected from the aluminum chelate compounds represented by the above general formula are mixed with alcohol as a medium and then filtered. Separately, a second step of drying to form a coating layer made of the aluminum chelate compound on the surface of the coating layer made of squaric acid, a method for producing magnetic particle powder,

The magnetic particle powder and the anthraquinone skeleton polyol represented by the above general formula are mixed with alcohol as a medium, and then filtered and dried to form a coating layer of the anthraquinone skeleton polyol on the particle surface of the magnetic particles. Step, and one or more kinds of aluminum chelate selected from magnetic particle powder in which a coating layer made of anthraquinone skeleton polyol is formed on the particle surface through the first step and an aluminum chelate compound represented by the above general formula. A compound characterized in that it comprises a second step of forming a coating layer comprising the aluminum chelate compound on the surface of the coating layer comprising the anthraquinone skeleton polyol by mixing the compound with alcohol as a medium, filtering and drying. Particle powder manufacturing method,

The magnetic particle powder, squaric acid, and the anthraquinone skeleton polyol represented by the above general formula are mixed with alcohol as a medium, and then filtered and dried to form a coating layer of the anthraquinone skeleton polyol on the surface of the magnetic particles. And a magnetic particle powder having a coating layer formed of squaric acid and anthraquinone skeleton polyol on the surface of the particle through the first step, and an aluminum chelate compound represented by the general formula Alternatively, two or more kinds of aluminum chelate compounds are mixed with alcohol as a medium, and then filtered and dried to form a coating layer made of the aluminum chelate compound on the surface of the coating layer made of the squaric acid and the anthraquinone skeleton polyol. A magnetic particle powder characterized by comprising a second step Granulation method,

A magnetic recording medium in which a magnetic recording layer comprising magnetic particle powder and a binder resin is formed on a non-magnetic support, wherein the magnetic particle powder is any one of claims 1 to 3. A magnetic recording medium characterized by being the magnetic particle powder described above.

First, the magnetic particle powder according to the present invention will be described.

The magnetic particle powder according to the present invention includes maghemite (γ-Fe ₂ O ₃ ) particles and magnetite (Fe ²⁺ _x F).
magnetic iron oxide particles such as e ³⁺ _{(8-2x) / 3} O ₄ (0 <x ≦ 1)) particles, and these magnetic iron oxide particles include Co and A other than Fe.
Particles containing different elements such as 1, Ni, P, Zn, Si and B, or particles obtained by depositing Co or the like on these magnetic iron oxide particles, metallic magnetic particles containing iron as a main component, and C other than iron.
iron alloy magnetic particles containing different elements such as o, Al, Ni, P, Zn, Si, and B, plate-like Ba ferrite particles, and a divalent metal (Co, Ni, Zn) as a coercive force reducing agent.
Etc.) and a tetravalent metal (Ti, Sn, Zr, etc.), and magnetic particles selected from plate-shaped composite ferrite particles and the like, wherein a square acid or an anthraquinone skeleton polyol or square acid is formed as a lower layer on the surface of the particles. The magnetic particles have a coating layer made of anthraquinone skeleton polyol, and a coating layer made of a specific aluminum chelate compound as an upper layer.

The squaric acid content of the magnetic particle powder according to the present invention is preferably 0.01 to 30% by weight, and more preferably 0.02 to 25% by weight, based on the total carbon content, calculated from the carbon content. % By weight. The content of the anthraquinone skeleton polyol is preferably 0.01 to 30% by weight with respect to the entire magnetic particle powder, converted from the carbon content.
More preferably, it is 0.02 to 25% by weight. In addition,
When both the squaric acid and the anthraquinone skeleton polyol are contained, the total content is preferably 0.02 to 30% by weight, more preferably 0, based on the total amount of the magnetic particle powder in terms of the carbon content. 0.02 to 25% by weight.
The content of the aluminum chelate compound is 0.01 to 30% by weight, preferably 0.02, calculated from the Al content.
~ 25% by weight.

The magnetic particle powder according to the present invention has an average particle size of 0.05 to 0.5 μm, preferably 0.1 to 0.4 μm.
Is. The shape may be any of a needle shape, a plate shape, a spherical shape, a granular shape, etc., and is preferably a needle shape. The axial ratio is 3 to 10, preferably 5 to 9, the BET specific surface area is 20 to 80 m ² / g,
It is preferably 25 to 60 m ² / g.

The magnetic particle powder according to the present invention has a coercive force Hc.
Is 500 to 3000 Oe, preferably 600 to 250
0 Oe, saturation magnetization σs is 60 to 200 emu / g, preferably 70 to 170 emu / g. Aged deterioration Δσs after 7 days ((saturation magnetization value before accelerated aging test) − (saturation magnetization value after 7 days of accelerated aging test)) is 10 emu / g or less, preferably 7 emu / g or less.

The magnetic particle powder according to the present invention exhibits good dispersibility in resins in which the polar group of the binder resin has either an acidic group or a basic group. Paint viscosity in kneading with binder resin (shear rate D = 1.92
/ Sec) is 1000 to 5500 cP , and the amount of increase in paint viscosity after 7 days ((paint viscosity before accelerated aging test)-
(Paint viscosity after 7 days of accelerated aging test) is 0 to 1200c
P.

Next, a method for producing the magnetic particle powder according to the present invention will be described.

The magnetic particle powder used in the present invention includes maghemite (γ-Fe ₂ O ₃ ) particles and magnetite (Fe).
Magnetic iron oxide particles such as ²⁺ _x Fe ³⁺ _{(8-2x) / 3} O ₄ (0 <x ≦ 1)) particles, and these magnetic iron oxide particles contain C other than Fe.
Particles containing different elements such as o, Al, Ni, P, Zn, Si, and B, or particles obtained by depositing Co or the like on these magnetic iron oxide particles, metallic magnetic particles containing iron as a main component, other than iron Of iron alloy magnetic particles containing different elements such as Co, Al, Ni, P, Zn, Si, and B, plate-like Ba ferrite particles, and a divalent metal (Co, N) as a coercive force reducing agent.
Magnetic particle powder composed of magnetic particles selected from plate-like composite ferrite particles containing i, Zn, etc.) and a tetravalent metal (Ti, Sn, Zr, etc.) can be used.

The magnetic particle powder has an average particle size of 0.05
~ 0.5 μm, preferably 0.1-0.4 μm,
The shape may be needle-like, plate-like, granular or spherical,
It is preferably needle-shaped. BET specific surface area is 20-80m
² / g, preferably 25 to 60 m ² / g.

The coercive force of the magnetic particle powder is 500 to 30.
00 Oe, preferably 600 to 2500 Oe, the saturation magnetization σs is 60 to 200 emu / g, preferably 70 to 17
It is 0 emu / g.

The squaric acid used in the present invention is the compound of Chemical formula 13, and specifically, commercially available 3,4-dihydroxy-3-cyclobutene-1,2-dione (manufactured by Tokyo Chemical Industry Co., Ltd.) is used. Can be used.

[Chemical 13]

The coating of the magnetic particles of squaric acid on the particle surface is carried out by mixing the magnetic particle powder and squaric acid in water or alcohol as a medium. Specifically, a method of directly adding squaric acid powder to an aqueous suspension or an alcohol suspension of magnetic particle powder, and an aqueous squaric acid solution or a squaric acid alcohol solution is added to an aqueous suspension of magnetic particle powder. A method, a method of directly adding magnetic particle powder to a square acid aqueous solution or a square acid alcohol solution, and a method of mixing an aqueous solution or alcohol solution of square acid and an aqueous suspension or alcohol suspension of magnetic particle powder are selected. After mixing by any one of the methods described above and sufficiently stirring to cover the surface of the particles with squaric acid, filtration and drying are performed to obtain a magnetic particle powder in which the surface of the particles is covered with squaric acid. The range of addition temperature is 25 to 60 ° C., preferably 2
It is 5-40 degreeC.

Squaric acid is usually in a powder state, and in the coating treatment, it may be added directly or may be dissolved in water or alcohol in advance to form a solution.
The method of adding as a solution is preferable. When added as a solution, the solution concentration is 0.1 to 50 g /
1, preferably 0.5 to 10 g / l.

When the commercially available squaric acid is used, the amount added is 0.01 to 30.0% by weight, preferably 0.02 to 25.0% by weight, based on the magnetic particle powder. 0.
When it is less than 01% by weight, the effect of fixing the coating layer made of the aluminum chelate compound cannot be obtained in the next step. When it exceeds 30.0% by weight, the obtained effect is saturated, and rather, it exists separately from the magnetic particle powder, which causes deterioration of various characteristics, which is not preferable.

As the anthraquinone skeleton polyol used in the present invention, those having the following general formula 14 in which anthraquinone is the main skeleton and the total number of hydroxyl groups is 2 to 4 can be used.

[Chemical 14]

Specific examples of the anthraquinone skeleton polyol include alizarin, quinizarin, chrysazine, purpurin, purpuroxanthin, and the like.
Alizarin, 1,2-
dihydroxyxanthraquinone),

[Chemical 15]

The quinizarin shown in Chemical formula 16
rin, 1,4-dihydroxyxanthraqu
inone),

[Chemical 16]

Chrysaz shown in Chemical formula 17
in, 1,8-dihydroxyxanthraqui
none),

[Chemical 17]

Purpuri shown in Chemical formula 18
n, 1,2,4-trihydroxanthraq
uinone),

[Chemical 18]

Purpuroxanthin (pur
puroxanthin, 1,3-dihydroxy
anthraquione) or the like can be used.

[Chemical 19]

The coating with the anthraquinone skeleton polyol is carried out by mixing the magnetic particle powder and the anthraquinone skeleton polyol with alcohol as a medium. Specifically, an alcohol suspension of magnetic particle powder and an alcohol solution of anthraquinone skeleton polyol are mixed and sufficiently stirred, then filtered and dried to obtain magnetic particle powder in which the particle surface of the anthraquinone skeleton polyol is coated. . The range of addition temperature is 25 to 60 ° C., preferably 25 to 40
℃.

Since the above-mentioned anthraquinone skeleton polyol is usually in a powder state, it is preferable to use a solution prepared by dissolving it in alcohol such as ethanol in advance for coating.

The solution concentration is 0.1 to 50 g / l, preferably 0.5 to 10 g / l. The addition amount of the anthraquinone skeleton polyol is 0.
01 to 30.0% by weight, preferably 0.02 to 25.0
% By weight. If it is less than 0.01% by weight, the effect of fixing the aluminum chelate coating layer in the next step cannot be obtained. When it exceeds 30.0% by weight, the obtained effect is saturated, and rather, it exists separately from the magnetic particle powder, which causes deterioration of various characteristics, which is not preferable.

As the aluminum chelate compound used in the present invention, those having the following general formula 20 can be used.

[Chemical 20]

Specific examples of the aluminum chelate compound used in the present invention include commercially available aluminum-di-n.
-Butoxide-monoethylacetoacetate, aluminum-di-isopropoxide-monoethylacetoacetate, aluminum-mono-n-butoxide-diethylacetoacetate (all Hope Pharmaceutical Co., Ltd.) and aluminum monoacetylacetonate bis (ethyl) Acetoacetate), aluminum tris (acetylacetonate) (above, manufactured by Kawaken Fine Chemicals Co., Ltd.), alkyl acetoacetate aluminum diisopropylate (above, manufactured by Ajinomoto Co., Inc.) and the like can be used.

The coating with the aluminum chelate compound is carried out by mixing the magnetic particle powder obtained through the previous step and the aluminum chelate compound with alcohol as a medium. Specifically, since the specific aluminum chelate compound is a viscous liquid, a method of adding it as an alcohol solution of isopropyl alcohol or the like to an alcohol suspension of magnetic particle powder or magnetic particles in an alcohol solution of an aluminum chelate compound is used. The powders are mixed by a method of suspension, sufficiently stirred, filtered and dried to form a coating layer made of the specific aluminum chelate compound on the surface of the coating layer made of the squaric acid or the anthraquinone skeleton polyol.

When the specific aluminum chelate compound is added as an alcohol solution, its concentration is 0.1 to 50 g.
/ L, preferably 0.5 to 20 g / l. The addition temperature range is 25 to 60 ° C, preferably 25 to 40 ° C.

When the specific aluminum chelate compound is used, the addition amount is 0.01 with respect to the magnetic particle powder.
˜30.0 wt%, preferably 0.02 to 25.0 wt%. If the amount is less than 0.01% by weight, it is one of the objects of the invention that the resin having a polar group is not well compatible with the resin and good dispersibility and dispersion stability cannot be obtained. 30.0
When the content is more than 10% by weight, the obtained effect is saturated, and rather, it exists separately from the magnetic particle powder, which causes deterioration of various properties, which is not preferable.

Next, the magnetic recording medium according to the present invention will be described.

In the magnetic recording medium according to the present invention, a magnetic recording layer comprising the magnetic particle powder according to the present invention and a binder resin is formed on a non-magnetic substrate, and the magnetic particle powder in the magnetic recording layer is formed. The binder resin is 10 to 4 with respect to 100 parts by weight.
0 parts by weight, preferably 20 to 30 parts by weight, and other additives 10 to 30 parts by weight, preferably 15 to 25 parts by weight.

The magnetic characteristics of the magnetic recording medium according to the present invention have a coercive force of 500 to 3000 Oe, preferably 600 to 25.
00 Oe, saturation magnetic flux density of 1600 to 4000 G, preferably 2000 to 3500 G, residual magnetic flux density of 1300
~ 3200G, preferably 1500-3000G. The squareness ratio is 0.80 or more, preferably 0.83 or more. The degree of orientation is 3.00 or more, preferably 3.40 or more.

The tape characteristics of the magnetic recording medium according to the present invention have a surface roughness Ra of 30 nm or less, preferably 20 nm or less, and a glossiness (45 ° gloss) of 125% or more, preferably 140% or more before calendering. After calendering, the surface roughness Ra is 10 nm or less, preferably 7 nm or less, and the gloss (45 ° gloss) is 170% or more, preferably 18
It is 0% or more. Durability is 15 minutes or more, preferably 20
More than a minute.

A method of manufacturing the magnetic recording medium according to the present invention will be described.

The magnetic recording medium according to the present invention comprises 100 parts by weight of the magnetic particle powder according to the present invention and 10 to 4 binder resins.
0 parts by weight, preferably 20 to 30 parts by weight, and 10 to 30 parts by weight of other additives optionally added, preferably 1
It is obtained by kneading and dispersing 5 to 25 parts by weight and a solvent to obtain a magnetic coating composition, coating the magnetic coating composition on a non-magnetic support, magnetic field orientation and drying.

As the binder resin in the present invention, vinyl chloride-vinyl acetate copolymers, vinyl chloride-vinyl acetate-maleic anhydride copolymers, vinylidene chloride, which are currently widely used in the production of magnetic recording media, Polyurethane resin, styrene-butadiene copolymer, butadiene-acrylonitrile copolymer, polyvinyl butyral, cellulose derivative such as nitrocellulose, polyester resin, synthetic rubber resin such as polybutadiene, epoxy resin, polyamide resin, polyisocyanate, electron beam curing Acrylic urethane resin or the like and a mixture thereof can be used.

The binder resin in the present invention is mainly composed of a binder resin containing a binder resin having a polar group of an acidic group or a basic group. As the acidic group, a carboxyl group (-COOM (M = H, Li, Na, K)),
A sulfonic acid group _{(-SO 3 M (M = H} , Li, Na,
K)), a phosphonic acid group _{(-PO 3 M 2 (M =} H, Li,
Na, K)), hydroxyl (-OH), an mercapto group (-SH), sulfinic acid group _{(-SO 2 M (M = H} ,
Li, Na, K)), phosphinic acid group (-PO ₂ M
₂ (M = H, Li, Na, K), a glycidyl group (epoxy group) (—CH ₂ —CHOCH ₂ ), and the basic group is an ammonium group (N ⁺ RR′R ″ X).
^- (X = OH, Cl, Br, I; R, R ', R "= C _n
H _{2n + 1} n = 0 to 20)), phosphonium group (P ⁺ R
^{R'R "X - (X = OH} , Cl, Br, I; R, R ',
R ″ = C _n H _{2n + 1} n = 0 to 20)), an amino group (—N
RR ′ (R, R ′ = C _n H _{2n + 1} n = 0 to 20)),
A phosphino group (-PRR '(R, R' = C n H 2n + 1
n = 0~20)), a pyridinium group (-C ₅ H ₄ N ⁺ R
X ⁻ (X = OH, Cl, Br, I; R = C _n H _{2n + 1} n
= 0-20)), piperidinium group (-C ₅ H ₉ N ⁺ R
^{R'X - (X = OH, Cl} , Br, I; R, R '= C
_n H _{2n + 1} n = 0 to 20)), a pyrrolidinium group (-C
₄ H ₇ N ⁺ RR′X ⁻ (X = OH, Cl, Br, I;
R, R ′ = C _n H _{2n + 1} n = 0 to 20)).

The preferred range of the polar group concentration of the binder resin used in the present invention is 10 to 200 mmol / kg .
Yes , and more preferably 35 to 150 mmol / kg. When the amount is less than 10 mmol / kg, the polar groups adsorbed on the surface of the magnetic particles are too small, resulting in poor dispersion of the magnetic particle powder in the resin. This may rather deteriorate the dispersibility of the magnetic particle powder.

As the non-magnetic substrate material in the present invention,
Polyethylene terephthalate, polyethylene, polypropylene, polycarbonate, polyethylene naphthalate, which are currently widely used in the manufacture of magnetic recording media,
Synthetic resin films such as polyamide, polyamide-imide, polyimide, polysulfone, and metal foils and plates such as aluminum and stainless steel, and various papers can be used.

Other commonly used lubricants, abrasives, antistatic agents, coloring agents and the like may be added.

In kneading and dispersing the magnetic coating material of the present invention, for example, a twin-screw kneader, a twin-screw extruder, a pressure kneader, a two-roll mill, a three-roll mill or the like can be used. A ball mill, sand grinder, attritor, disper, homogenizer, ultrasonic disperser or the like can be used.

A gravure coater, a reverse roll coater, a slit coater, a die coater or the like can be used in applying the magnetic coating material of the present invention. The applied sheet can be magnetically oriented by a facing magnet arrangement, solenoid magnet orientation, or the like. Further, it is desirable to carry out calendering (smoothing) in order to improve the smoothness of the coating film surface. As a method therefor, there can be used a method of smoothing the surface of the coating film by passing a material having a coating film formed on a substrate between a pressure-heated metal roll and an elastic roll.

[0064]

BEST MODE FOR CARRYING OUT THE INVENTION A typical embodiment of the present invention is as follows.

The average major axis diameter, average minor axis diameter of particles in the following embodiments and examples and comparative examples of the present invention,
All the axial ratios are shown by the average value of the numerical values measured from electron micrographs. The specific surface area is shown by the value measured by the BET method.

The coating amount of the square acid and the anthraquinone skeleton polyol is "Horiba Metal Carbon / Sulfur Analyzer EMI
"A-2200" (manufactured by Horiba, Ltd.) was used to calculate and show the amount of carbon.

The coating amount of the aluminum chelate compound was measured by X-ray fluorescence analysis (model 3063M, Rigaku Denki Kogyo Co., Ltd.).
It was calculated and shown from the amount of Al measured by M.D.

The magnetic characteristics are as follows: "Vibration sample magnetometer VSM-
3S-15 "(manufactured by Toei Industry Co., Ltd.) was used, and the maximum external magnetic field was 10 kOe. Deterioration of saturation magnetization with time Δσ
s is indicated by the difference between the measured value of the saturation magnetization σs after 7 days and the initial saturation magnetization σs under the environment of the temperature of 60 ° C. and the relative humidity of 90%.

The coating viscosity was 25 ° C. and the shear rate D = 1.
The viscosity at 92 (/ sec) is measured by the E-type viscometer (VISC
ONIC EMD: manufactured by Tokyo Keiki Co., Ltd.). Further, the viscosity of the paint after 7 days was measured and used as an index of dispersion stability.

The durability is determined by the media durability tester MDT-3000 (Steinberg Assoc).
iates), using a relative speed of 16 m / sec,
The measured value (minute) at a load of 200 gw is shown.

The surface glossiness (45 ° gloss) of the coating film is
It is a value measured using a gloss meter UGV-5D (manufactured by Suga Test Instruments Co., Ltd.), and the value when the standard plate gloss is 86.3% is shown in%.

The surface roughness of the coating film obtained by applying the magnetic coating material to the PET film is shown by the value measured by a surface shape measuring instrument (Surfcom 575A: manufactured by Tokyo Seimitsu Co., Ltd.).

<Production of Magnetic Particle Powder> (First Step) Squaric Acid (3,4-Dihydroxy-3-
Cyclobutene-1,2-dione (Tokyo Chemical Industry Co., Ltd.)
100 g) was added to 2 liters of pure water in advance and water was added to the aqueous solution of squaric acid to make 10 liters, which were well stirred. The concentration of square acid at this time is 10 g / l
Met.

1 kg of metal magnetic particle powder containing iron as a main component and having an average particle size of 0.2 μm in 10 l of the above-mentioned aqueous solution of squaric acid.
Was gradually added, mixed and stirred for 30 minutes with a homomixer, filtered and dried to coat the particle surface of the metal magnetic particles containing iron as a main component with squaric acid.

The metal magnetic particle powder containing iron as the main component had a coating amount of squaric acid converted from the carbon content of 1.0% by weight.

(Second step) Metal magnetic particle powder 1k containing iron as a main component whose surface is coated with squaric acid.
g slowly in 10 l of isopropyl alcohol,
The mixture was stirred for 30 minutes with a homomixer to prepare a suspension. After the temperature of this suspension was raised to 60 ° C., aluminum-di-n-
75 g of a 10 wt% isopropyl alcohol solution of butoxide monoethyl acetoacetate was gradually added. After the addition, the mixture was further stirred for 30 minutes, filtered and dried to coat the surface of the particles with the aluminum chelate compound.

The metal magnetic particle powder containing iron as the main component had a coating amount of the aluminum chelate compound of 0.75% by weight calculated from the Al content.

The coercive force of the obtained metal magnetic particle powder containing iron as the main component was 1635 Oe, and the saturation magnetization was 129 em.
The test results of u / g, squareness ratio 0.49, and accelerated aging are as follows:
Deterioration of coercive force with time after 1 week in an environment of a temperature of 60 ° C. and relative humidity of 90% was 13 Oe, and deterioration of saturation magnetization with time Δ
[sigma] s was 7.7 emu / g, and was superior in oxidation stability to the metal magnetic particle powder containing iron as the main component obtained in Comparative Example 1 below.

As for the dispersibility in the resin, when the polar group is a sulfonic acid group (acidic group), the paint viscosity is 3000 cp and the dispersibility is good, and the paint viscosity after 7 days is 3800.
There was almost no change in viscosity with cp, and the dispersion stability was excellent. If the polar group is a basic group, the paint viscosity is 48.
The viscosity was 00 cp and the dispersibility was good, and the viscosity of the paint after 7 days was 5400 cp, showing almost no change in the viscosity, and the dispersion stability was excellent.

<Production of Magnetic Recording Medium> Metal magnetic particles containing iron as a main component and having a coating layer of squaric acid as a lower layer and a coating layer of an aluminum chelate compound as an upper layer on the surface of the particles obtained by the above process. magnetic particles 100 parts by weight of a vinyl chloride - vinyl acetate - vinyl alcohol copolymer (polar group: -SO ₃ Na, polar group concentration 60 mmol / kg) 12.5 parts by weight, 1 part by weight of myristic acid, cyclohexanone 30 weight Parts, 7 parts by weight of alumina powder, carbon black particle powder # 3250
(Mitsubishi Kasei Co., Ltd., particle size 28 nm, BET specific surface area 8
00 m ² / g) 3 parts by weight using a kneader for 30 minutes, and then the mixture was diluted with 76.4 parts by weight of toluene, 137.4 parts by weight of methyl ethyl ketone and 31 parts by weight of cyclohexanone, and then diluted. The mixture was mixed and dispersed by a sand grinder for 3 hours.

Polyurethane resin (polar group: —SO ₃ Na, polar group concentration 80 mmol / kg) was added to the mixed dispersion.
After adding 41.7 parts by weight of a methyl ethyl ketone-toluene solution containing 12.5 parts by weight of solid content of the mixture and mixing for 30 minutes, the filtered product obtained by filtering was added with E-31 (trifunctional low molecular weight isocyanate compound ( Takeda Pharmaceutical Co., Ltd. 5
By mixing parts by weight, a magnetic coating material was obtained.

The magnetic coating material obtained was applied onto a polyester base film having a thickness of 14 μm, and then 200 kg
After calendering at a pressure of / cm @ 2 and then drying to form a magnetic layer having a thickness of 4 .mu.m,
A magnetic tape was produced by cutting into a width of 1/2 inch.

[0083] The magnetic properties of the magnetic tape, calendar
Coercive force before treatment is 1650 Oe and residual magnetic flux density Br is 2
It was 600 Gauss and square type (Br / Bm) 0.86. The orientation was 3.45, the surface gloss (45 ° gloss) was 145%, and the surface roughness Ra was 20 nm.

[0084]

The important point in the present invention is that the binder resin used in the coating type magnetic recording medium is excellent in dispersibility even when the polar group contained in the binder resin is either an acidic group or a basic group, and is excellent in oxidation stability. It is a fact that a magnetic particle powder is obtained which is excellent in deterioration of magnetic properties over time.

The present inventors consider the above facts as follows. That is, by forming a coating layer made of squaric acid or anthraquinone skeleton polyol as a lower layer on the particle surface, it is possible to improve the oxidation stability,
Moreover, when the upper layer of the aluminum chelate compound is coated, the lower layer has the coating layer made of squaric acid or anthraquinone skeleton polyol, thereby forming a chemical bond with the aluminum chelate compound, and the coating layer made of the aluminum chelate compound. We believe that we can solidify. Furthermore, by coating the upper layer with an aluminum chelate compound, since aluminum is an amphoteric metal, the binder resin is well compatible with both acidic groups and basic groups, improving dispersibility. I think I was able to do it.

On the other hand, when only square acid or anthraquinone skeleton polyol is coated in a single layer, as shown in Comparative Examples 2 and 3 below, the square acid and anthraquinone skeleton polyol are contained in the binder resin. Familiarity with polar groups is small and sufficient dispersibility cannot be obtained. When only a single layer of aluminum chelate was coated, as shown in Comparative Example 5 below, the aluminum chelating agent was likely to come off the particle surface, sufficient dispersibility in the binder resin could not be obtained, and oxidation was difficult. It becomes inferior in stability.

On the other hand, when the coating order is reversed, as shown in Comparative Examples 7 and 8 below, when the aluminum chelate compound is coated on the surface of the particle as the lower layer, the aluminum chelate compound is easily separated from the surface of the particle. As a result, it will come off with the squaric acid or anthraquinone skeleton polyol of the coating layer above it, so that it will not function effectively and sufficient dispersibility and oxidation stability will not be obtained. Also,
When squaric acid or anthraquinone skeleton polyol is present in the upper coating layer, the compatibility with the binder resin is small and the dispersibility is not sufficient.

[0088]

EXAMPLES Examples and comparative examples of the present invention will be given below.

Examples 1-32, Comparative Examples 1-24; <Production of magnetic particle powder> Examples 1-14, Comparative Examples 1-8

Example 1 (First Step) Alizarin alcohol solution prepared by adding 100 g of alizarin (1,2-dihydroxyanthraquinone (manufactured by Tokyo Chemical Industry Co., Ltd.) to 2 l of ethyl alcohol in advance was made up to 10 l, and well. The mixture was stirred, and the concentration of alizarin at this time was 10 g / l.

To 10 l of the above alcohol solution of alizarin, 1 kg of powder of metal magnetic particles containing iron as a main component and having an average particle size of 0.15 μm was gradually added, and mixed and stirred for 30 minutes with a homomixer, followed by filtration and drying. Then, the particle surface of the metal magnetic particles containing iron as a main component was pulverized and coated with alizarin.

The metal magnetic particle powder containing iron as the main component had a coating amount of alizarin converted from the carbon content of 1.00% by weight.

(Second Step) Next, 1 kg of metal magnetic particle powder containing iron as a main component whose particle surface is coated with alizarin is gradually added to 10 l of isopropyl alcohol and stirred for 30 minutes with a homomixer. A suspension was made. After heating this suspension to 60 ° C., 75 g of a 10 wt% isopropyl alcohol solution of aluminum-di-n-butoxide monoethylacetoacetate was gradually added as an aluminum chelate compound while stirring. After the addition, the mixture was further stirred for 30 minutes, filtered and dried to coat the surface of the particles with the aluminum chelate compound.

In the obtained metal magnetic particle powder containing iron as the main component, the coating amount of the aluminum chelate compound calculated from the Al content was 0.75% by weight.

The metal magnetic particle powder containing iron as a main component thus obtained has an average particle diameter of 0.15 μm and a BET specific surface area of 4
7 m ² / g, coercive force 1660 Oe, saturation magnetization 125
emu / g, squareness ratio 0.49, accelerated aging test result is 1 in the environment of temperature 60 ° C and relative humidity 90%.
The time-dependent deterioration of coercive force after 10 weeks was 10 Oe, and the time-dependent deterioration of saturation magnetization Δσs was 6.1 emu / g, which is stable against oxidation as compared with the iron-based metal magnetic particle powder obtained in Comparative Example 1 below. It was excellent in nature.

As for the dispersibility in the resin, when the polar group of the binder resin is an acidic group, the paint viscosity is excellent at 4500 cp, and the paint viscosity after 7 days is 5300 cp, showing almost no change in viscosity and dispersion. It was excellent in stability. When the polar group is a basic group, the paint viscosity is 5300 cp
With excellent dispersibility, the paint viscosity after 7 days is 62
There was almost no change in viscosity from 00 cp, and the dispersion stability was excellent.

Example 2 (First step) Squaric acid (3,4-dihydroxy-3-)
Cyclobutene-1,2-dione (Tokyo Chemical Industry Co., Ltd.)
50 g of alizarin) and 50 g of alizarin (1,2-dihydroxyanthraquinone (manufactured by Tokyo Kasei Kogyo Co., Ltd.)) are added to 2 l of ethyl alcohol in advance, and ethyl alcohol is further added to an alcohol solution of squaric acid and alizarin. It was adjusted to 10 liters and well stirred.
At this time, the concentration of squaric acid was 5.0 g / l and the concentration of alizarin was 5.0 g / l.

To 10 l of the above-mentioned alcohol solution of squaric acid and alizarin, 1 kg of metal magnetic particle powder containing iron as the main component and having an average particle diameter of 0.15 μm was gradually added, and after mixing and stirring for 30 minutes with a homomixer, After filtering and drying, the surface of the metal magnetic particles containing iron as a main component was coated with squaric acid and alizarin.

The obtained metallic magnetic particle powder containing iron as a main component had a coating amount of squaric acid of 0.5% by weight and an coating amount of alizarin of 0.5% by weight, which were calculated from the carbon content.

(Second Step) Next, 1 kg of powdered metal magnetic particles containing iron as a main component whose surface was coated with squaric acid and alizarin was mixed with isopropyl alcohol 1.
The mixture was gradually added to 0 l and stirred with a homomixer for 30 minutes to prepare a suspension. After heating this suspension to 60 ° C., 75 g of a 10 wt% isopropyl alcohol solution of aluminum-di-n-butoxide monoethylacetoacetate was gradually added as an aluminum chelate compound while stirring. After the addition, the mixture was further stirred for 30 minutes, filtered and dried to coat the surface of the particles with the aluminum chelate compound.

The metal magnetic particle powder containing iron as the main component had a coating amount of the aluminum chelate compound of 0.75% by weight calculated from the Al content.

The metal magnetic particle powder containing iron as the main component obtained here has an average particle size of 0.15 μm and a BET specific surface area of 4
6 m ² / g, coercive force 1650 Oe, saturation magnetization 121
The test results of emu / g, squareness ratio 0.49, and accelerated aging change show that the coercive force after one week has deteriorated by 12 Oe and the saturation magnetization has deteriorated by Δσs of 5 in an environment of temperature 60 ° C. and relative humidity 90%. It was 0.4 emu / g, and was excellent in oxidation stability as compared with the metal magnetic particle powder containing iron as a main component obtained in Comparative Example 1 described later.

As for the dispersibility in the resin, when the polar group of the binder resin is an acidic group, the paint viscosity is excellent at 2800 cp and the paint viscosity after 7 days is 3400 cp, showing almost no change in viscosity and dispersion. It was excellent in stability. If the polar group is a basic group, paint viscosity 3800 cp
With excellent dispersibility, the paint viscosity after 7 days is 43
There was almost no change in viscosity from 00 cp, and the dispersion stability was excellent.

Examples 3 to 14, Comparative Examples 1 to 8 Type of particles to be treated, type of lower layer treated substance and addition amount,
Magnetic particle powders were obtained in the same manner as in the embodiment of the present invention, except that the type and amount of the upper-layer treated material were changed. The manufacturing conditions of the magnetic particle powder are shown in Tables 1 and 2, and the characteristics of the magnetic particle powder obtained are shown in Tables 3 and 4.

[0105]

[Table 1]

[0106]

[Table 2]

[0107]

[Table 3]

[0108]

[Table 4]

<Production of Magnetic Recording Medium> Examples 15 to 32, Comparative Examples 9 to 24 Types of magnetic particle powder, types of polar groups contained in the binder resin, polar group concentration and blending amount, types of fillers, solvents A magnetic recording medium was obtained by using the magnetic particle powder in the same manner as in the embodiment of the present invention except that the kinds and blended amounts, the blended amount of the lubricant, and the blended amount of the curing agent were changed. Manufacturing conditions of the magnetic recording medium are shown in Tables 5 and 6, and various characteristics of the obtained magnetic recording medium are shown in Tables 7 and 8.

[0110]

[Table 5]

[0111]

[Table 6]

[0112]

[Table 7]

[0113]

[Table 8]

[0114]

INDUSTRIAL APPLICABILITY The magnetic particle powder according to the present invention has excellent dispersibility regardless of whether the polar group of the binder resin used in the coating type magnetic recording medium is an acidic group or a basic group, and It is suitable for a magnetic recording medium for high-density recording because it has excellent oxidative stability and little deterioration of magnetic properties over time.

─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-5-225552 (JP, A) JP-A-5-225553 (JP, A) JP-B-6-4786 (JP, B2) (58) Field (Int.Cl. ⁷ , DB name) H01F 1/00-1/38 G11B 5/68-5/845

Claims (7)

(57) [Claims] 1. A magnetic particle having a coating layer consisting of two layers, a lower layer and an upper layer, on the surface of the particle, wherein the lower layer is a coating layer made of squaric acid, and the upper layer is aluminum represented by the following general formula 1. A magnetic particle powder comprising magnetic particles, which is a coating layer composed of one or more aluminum chelate compounds selected from chelate compounds. [Chemical 1] 2. A magnetic particle having a coating layer composed of a lower layer and an upper layer on the surface of the particle, wherein the lower layer is a coating layer composed of an anthraquinone skeleton polyol represented by the following general formula 2. ] A magnetic particle powder comprising magnetic particles, wherein the upper layer is a coating layer composed of one or more aluminum chelate compounds selected from the aluminum chelate compounds represented by the following general formula 3. [Chemical 3] 3. A magnetic particle having a coating layer consisting of a lower layer and an upper layer on the surface of the particle, wherein the lower layer is a coating layer comprising squaric acid and an anthraquinone skeleton polyol represented by the following general formula 4. , A magnetic particle powder comprising magnetic particles, wherein the upper layer is a coating layer composed of one or more aluminum chelate compounds selected from the aluminum chelate compounds represented by the following general formula (5). [Chemical 5] 4. A first step of forming a coating layer of squaric acid on the particle surface of the magnetic particles by mixing magnetic particle powder and squaric acid in water or alcohol as a medium, filtering and drying. A magnetic particle powder in which a coating layer made of squaric acid is formed on the particle surface via the first step and one or more aluminum chelate compounds selected from the aluminum chelate compounds represented by the following general formula (6): After mixing with alcohol as a medium, it is filtered off,
A method for producing magnetic particle powder, comprising a second step of drying to form a coating layer made of the aluminum chelate compound on the surface of the coating layer made of squaric acid. [Chemical 6] 5. A magnetic particle powder and an anthraquinone skeleton polyol represented by the following general formula 7 are mixed with alcohol as a medium, followed by filtration and drying to form a coating layer of the anthraquinone skeleton polyol on the particle surface of the magnetic particles. The first step of forming, and One or more aluminum chelate compounds selected from a magnetic particle powder having a coating layer made of an anthraquinone skeleton polyol formed on the particle surface via the first step and an aluminum chelate compound represented by the following general formula (8). Magnetic particles powder characterized by comprising a second step of forming a coating layer made of the aluminum chelate compound on the surface of the coating layer made of the anthraquinone skeleton polyol by filtering and drying with and using alcohol as a medium. Manufacturing method. [Chemical 8] 6. A magnetic acid powder, squaric acid, and anthraquinone skeleton polyol represented by the following general formula 9 are mixed with alcohol as a medium, and then filtered and dried to form square acid and anthraquinone skeleton on the particle surface of the magnetic particles. A first step of forming a coating layer made of a polyol, and One or more selected from a magnetic particle powder having a coating layer composed of squaric acid and anthraquinone skeleton polyol formed on the surface of the particle via the first step and an aluminum chelate compound represented by the following general formula 10. From the second step of forming a coating layer made of the aluminum chelate compound on the surface of the coating layer made of the squaric acid and the anthraquinone skeleton polyol by filtering the aluminum chelate compound with an alcohol as a medium, filtering and drying. A method for producing a magnetic particle powder, comprising: [Chemical 10] 7. A magnetic recording medium in which a magnetic recording layer composed of magnetic particle powder and a binder resin is formed on a non-magnetic support, wherein the magnetic particle powder is any one of claims 1 to 3.
2. A magnetic recording medium comprising the magnetic particle powder according to any one of 1.