JPS63210031A - Ferrite powder and magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain the titled powder which gives a medium excellent in regenerative output and signal noise ratio or the like and is excellent in magnetic characteristics and has a uniform fine powdery shape, by mixing two or more kinds of metallic acetylacetone incorporating barium acetylacetone and iron acetylacetone and hydrolyzing the mixture and thereafter calcining it. CONSTITUTION:Both two kinds of metallic acetylacetone consisting of barium acetylacetone and iron acetylacetone and metallic acetylacetone shown in a formula [M' shows monovalent - pentavalent metal such as Co, Ti, Sr, Al, Li, Na, Mg, Ca, Si, V, Cr, Mn, Ni, Cu, Zn, Y, Zr, Mo, Sn and Pb, (n) is 1-5] in accordance with necessity are prepared and mixed so that these are regulated to the final stoichiometric composition and the mixture is added into a solvent such as ethanol so that the concn. is regulated to 0.01-0.04mol./l. Then after heating this mixture under reflux, aq. ammonia is added and it is aged and thereafter heated at 80-100 deg.C to finish hydrolyzing reaction. The hydrolysate obtained by filtering the precipitate is calcined at the temp. and hour correspondent to an aimed product (e.g. at 800-1,300 deg.C for 1-2hr in the case of barium ferrite) in the atmosphere or the gaseous atmosphere regulated by N2 and O2.

Description

Detailed Description of the Invention ■ Background Technical Field of the Invention The present invention involves mixing two or more metal acetylacetones including Ba acetylacetone and Fe acetylacetone,
The present invention relates to a ferrite powder made of a uniform fine powder with good magnetic properties obtained by hydrolysis, and a magnetic recording medium containing this ferrite powder.

Prior art and its problems Conventionally, solid phase reaction method, wet coprecipitation method, and glass ceramic method are generally known as methods for producing ferrite fine particles.

Furthermore, in addition to these methods, the hydrolysis method of organometallic compounds is known to have many excellent features as a method for synthesizing amorphous materials.

This method is said to be particularly useful for synthesizing fine crystal particles because it allows a homogenization reaction at the micro level in a liquid state, and facilitates the formation of an amorphous state and the production of fine particles. Under these current circumstances, various proposals have been made regarding methods for producing ferrite fine particles by hydrolysis of organometallic compounds.

That is, the so-called metal alkoxide method, in which fine ferrite particles are produced by hydrolysis using two or more metal alkoxides (Japanese Unexamined Patent Publication No. 140721/1983),
No. 55-140722, No. 56-26726, No. 5
B-45115, 5B-45119, 58-1
No. 99724, production of barium ferrite from metal alkoxide, "Powder and Powder Metallurgy," Vol. 29, No. 5, July 982, etc.), and mixing metal alkoxide and metal acetylacetonate to form ferrite fine particles by hydrolysis. There have been proposals for manufacturing methods (JP-A-56-26727, JP-A No. 5B-45120, JP-A No. 5B-45121, etc.).

According to these proposals, the obtained fine particles will be highly active and have good sinterability, so the sintered body produced using these particles will have a sintered density that is lower than that obtained by the ordinary powder method. It is said to be larger than that using fine particles.

Moreover, in the above-mentioned proposed manufacturing method, it is possible to manufacture both so-called M-phase ferrite and W-phase ferrite. Among these, especially M-phase ferrite,
This material can be incorporated into a magnetic layer as magnetic powder and used as a magnetic recording medium for perpendicular recording or the like.

Normally, to manufacture a magnetic recording medium, a magnetic paint is applied onto a non-magnetic support, the magnetic powder is then oriented, and the paint is dried.

However, the ferrite powders obtained by the various manufacturing methods described above do not always have sufficiently satisfactory magnetic properties, particularly properties such as coercive force and residual magnetization.

Therefore, when this material is used in a magnetic recording medium, the medium characteristics cannot be said to be satisfactory, and improvements in these points are required.

■ Purpose of the invention The purpose of the present invention is to produce B by the hydrolysis method of organometallic compounds.
The object of the present invention is to obtain an a-ferrite powder having good magnetic properties, and to provide a magnetic recording medium containing this Ba-ferrite powder.

■ Disclosure of invention Such objects are achieved by the invention described below.

That is, in the first invention, Ba acetylacetone and Fe
This is a ferrite powder characterized by mixing two or more types of metal acetylacetone including acetylacetone, hydrolyzing the mixture, and then calcining the mixture.

Further, the second invention is a method of mixing two or more types of metal acetylacetones including Ba acetylacetone and Fe acetylacetone, hydrolyzing the mixture, and then baking it to obtain an M-phase ferrite powder, and combining this M-phase ferrite powder with a binder. A magnetic recording medium is characterized in that a magnetic coating material containing the following is coated on a non-magnetic support.

■Specific structure of the invention Hereinafter, a specific configuration of the present invention will be explained in detail.

In the present invention, two or more types of metal acetylacetones including Ba acetylacetone and Fe acetylacetone are mixed and a predetermined ferrite powder is obtained by hydrolysis.

Among ferrites, there is one called hexagonal M-phase Ba ferrite (BaFe120t
s).

Hereinafter, the Ba ferrite manufacturing method of the present invention will be explained in detail.

The starting material of the present invention is a mixture of two or more metal acetylacetones including Ba acetylacetone and Fe acetylacetone.

The above Ba acetylacetone is usually Ba (08H702
)2, and Fe acetylacetone is represented by Fe (C
8Ht 02 )s.

In this case, the metal acetylacetone mentioned above is usually one that does not have H2O as a coordinated water, but one that has coordinated water, such as Ba(C5Ht 02 )2 .4H,O, etc., may also be used.

Furthermore, other metal acetylacetones (Cs)IT 02 )n as shown below can also be added to the starting material, where n is from 1 to 5.

M' is 1 to 5 metals, specifically Co, Ti
, Sr%Al, Lj%Be, B.

Na, Mg, Si, Ca, Sc, V.

Cr, Mn%Ni%Cu%Zn%Ga%Ge.

As% Se% Rh2, Y, Zr% Nb, Mo, Cd
, In, Sn, Sb, Te%Cs, La.

Examples include Pb and Bi.

In addition, for Ti etc., in addition to the above, M'O-(Cs Ht 02 ) n-2-(1≦m
an/2).

The starting materials as described above are adjusted to the final product MJ@Ba ferrite as described below.

1) B a fist F e 2no
3n+1n: 4.0 to 6.0 (hereinafter the same) Starting material Ba (C5H,0□), etc. ii) Substituted product B
a Ferrite (1) B a ” Fe ” (2n-y) ” M
A"ly/2) M 8"(y/21" O(3n+
I+B a ” F e (2n-y) ” Me”y
” O(3n+lIB a ′F e (2n-yl
"MA2'"+2y/3)・MO" (y/31
"O+3n+1), etc. y: 1.0 to 2.5 MA, Ma, Mc, MD: One or more of the above-mentioned metals that can have respective ionic valences (2) Two or more of (1) at the same time Substituents intended to be combined, for example, the combination of MA''+MB'+ and Mc1.

Among these, in ii) above, 8 to 31 at% of Co"+Ti of Fe'+ ions
Those containing '+' are suitable for use in magnetic recording media.

In addition, in the present invention, the following W-phase Ba ferrite can be produced.

1) Ba2″″・MB″2 Fe″16027i
i) Substituted ferrite Ba”-(ME”11-ri MP”ri 2・F e “1
8027 M62◆, M22◆: Fe"◆, Zn2◆, Cu24"
, N t 2+, 0024″, etc., which is 1 of the metal that becomes divalent.
More than species z: 0~! The mixing ratio of these starting materials is adjusted so as to provide the desired final stoichiometric composition of the M-phase Ba ferrite, W-phase Ba ferrite, and the like.

After mixing a predetermined amount of raw materials in this manner, alcohol, especially ethanol, is used as a solvent until the total amount of the metal acetylacetone containing Ba and Fe is 0.01 to 0.04.
Add so that it becomes about mol/J2-. after that,
Heat and reflux at the ethanol boiling point for about 1 hour. Thereafter, it is naturally cooled, left to stand for about one night, and then added at room temperature in an amount of about 1.5 Il per 1 mol of aqueous ammonia and the metal acetylacetone.

Then, after aging for about 2 days, that is, about 40 to 48 hours, a heating reaction is carried out at 80 to 100° C. for about 3 hours to complete the hydrolysis.

Thereafter, the precipitate precipitated in the solvent by hydrolysis is separated by suction, filtration, and dried. The material that hardens during drying is loosened into powder and used as a fired sample. Usually, the hydrolysis product is amorphous and needs to be crystallized by heat treatment (calcination) or the like.

Firing is normally performed in the atmosphere or in an atmosphere in which the oxygen partial pressure of N2+02 mixed gas is adjusted.

When adjusting the oxygen partial pressure, the partial pressure is P02/(p 0
2+P N2) is preferably about 10-5 to the value in the atmosphere.

Such a firing atmosphere should be appropriately selected depending on the desired ferrite composition to be obtained, but usually M phase Ba
In the case of ferrite, it is preferable to carry out the process in the atmosphere. In addition, in the case of W-phase Ba ferrite, N2+0□
An atmosphere in which the oxygen partial pressure of the mixed gas is adjusted, for example, P02/
(PO2+PN2)=10-' may be fired in the atmosphere.

The firing temperature and time are also appropriately selected depending on the desired ferrite composition.
050°C for about 1 to 2 hours, 1200 to 1400°C for W phase Ba ferrite, preferably 1200 to 130°C.
0°C for 3 to 5 hours. The suitability of this firing temperature affects magnetic properties, particularly saturation magnetization, residual magnetization, coercive force, and the like. In addition, in the case of W phase, 800 to 1
Calcination may be performed before firing at 200° C. for 1 to 2 hours.

The particle size of the obtained powder is approximately 500λ to several tens of λ, particularly in the case of M phase Ba ferrite, approximately 500λ to 1000λ.

In addition, as M-phase Ba ferrite for magnetic recording media,
A particle size of 400 to 700 particles and a plate ratio of about 1 to 3.5 are suitable.

The Ba ferrite powder of the present invention obtained by the manufacturing method described in detail above has excellent magnetic properties compared to that obtained by the conventional manufacturing method.

In this case, in M-phase Ba ferrite, Ba0(Fe2o
3) It is confirmed by X-ray diffraction that it has a composition of q, (q is 4 to 6).

As described above, the substituted product may be prepared by mixing a predetermined amount of a metal acetylacetone compound containing these elements as a starting material. Alternatively, a predetermined amount of an oxide, carbonate compound, halogen compound, etc. containing these elements may be added and mixed during firing.

When such ferrite powder is used as a magnetic powder for a magnetic recording medium, good results are shown in terms of the medium properties.

That is, for example, the signal-to-noise ratio characteristics are significantly improved.

Magnetic recording media produced using such powder usually have a magnetic layer on a non-magnetic support, and the magnetic layer contains Ba ferrite powder produced by the above manufacturing method and the following binder. Contains.

Such a magnetic recording medium is manufactured as follows.

That is, first, ferrite powder is made by the above manufacturing method, and then a binder, a solvent, etc. are mixed with it,
Create magnetic paint.

This magnetic paint is applied onto a substrate such as a polyester film using methods such as gravure coating, reverse roll coating, air knife coating, air doctor coating, blade coating, kiss coating, and spray coating, and is applied horizontally or vertically as necessary. It may be subjected to orientation treatment using a magnetic field or the like in the direction, dried, and preferably cured by radiation according to a conventional method. Then, a back coat and a top coat may be provided as necessary.

The orientation treatment follows a conventional method and employs various methods to obtain the predetermined perpendicular squareness ratio and coercive force as described above.

For example, permanent magnets, direct current magnets, and alternating current magnetic fields are typically used as orientation methods, and various combinations of these are used, such as vertical and horizontal combinations, horizontal orientation, permanent magnets or combinations of direct current magnetic fields and alternating current magnetic fields, mechanical Various orientations can be used, such as mechanical orientation, mechanical orientation, combinations of the above, natural orientation, etc.

Among these, mechanical orientation and horizontal orientation are particularly preferred in the present invention.

The magnetic field strength used for orientation is preferably 1000 to 6000G.

The coating film thickness is usually about 0.2 to 10.

In the recording medium of the present invention, a high magnetic permeability metal thin film such as permalloy or an undercoat layer of various coatings may be further provided between the support and the magnetic layer. These may be used in combination.

The undercoat layer of the coating film contains a thermosetting resin or radiation curing compound, a conductive pigment, an inorganic filler,
Lubricants, surfactant dispersants, etc. are included as necessary.

Various plasma polymerized films are also useful.

The magnetic paint, which is the raw material for the magnetic coating film of the magnetic recording medium manufactured in this way, contains barium ferrite magnetic powder made by a prescribed manufacturing method as described above, a binder, and if necessary, a solvent. .

The binder used when making magnetic powder into a magnetic paint is a radiation-curable resin, a thermoplastic resin, a thermosetting or reactive resin, or a mixture thereof. Preferably, a radiation-curable resin is used.

The thermoplastic resin has a softening temperature of 150°C or lower, an average molecular weight of 10,000 to 200,000, and a degree of polymerization of 200 to 200.
It is about 2,000.

Thermosetting resins or reactive resins have such a degree of polymerization, and by heating after coating and drying,
The molecular weight becomes infinite due to reactions such as condensation and addition. Among these resins, those that do not soften or melt before the resin is thermally decomposed are preferred.

Specifically, for example, phenol resin, epoxy resin, polyurethane curable resin, urea resin, butyral resin, formal resin, melamine resin, alkyd resin, silicone resin, acrylic reaction resin, polyamide resin, epoxy-polyamide resin, saturated polyester resin. , mixtures of polycondensation resins such as urea formaldehyde resins or high molecular weight polyester resins and isocyanate prepolymers, mixtures of methacrylate copolymers and diisocyanate prepolymers, mixtures of polyester polyols and polyisocyanates, low molecular weight glycols/high molecular weights Diol/triphenylmethane triisocyanate mixtures, mixtures of the above condensation resins and crosslinking agents such as isocyanate compounds, vinyl chloride-vinyl acetate (including carboxylic acid-containing), vinyl chloride-vinyl alcohol-
Mixtures of vinyl copolymer resins such as vinyl acetate (including those containing carboxylic acids), vinyl chloride-vinylidene chloride, vinyl chloride-acrylonitrile, vinyl butyral, vinyl formal, etc., and crosslinking agents, fibers such as nitrocellulose, cellulose acetobutyrate, etc. mixture of base resin and crosslinking agent,
Mixtures of synthetic rubber systems such as butadiene-acrylonitrile and crosslinking agents, as well as mixtures thereof, are preferred.

and, in particular, mixtures of epoxy resins, butyral resins, and phenolic resins, mixtures of epoxy resins, polyvinyl methyl ether, and methylol phenol ether as described in U.S. Pat. No. 3,058,844;
A mixture of a bisphenol A type epoxy resin and an acrylic ester or methacrylic ester polymer described in No. 9-131101 is preferred.

To cure such a thermosetting resin, it is generally necessary to heat it in a heating oven at 50 to 80°C for 6 to 100 hours.

As the binder, it is particularly preferable to use a hardened radiation-curable compound, that is, a radiation-curable resin.

Specific examples of radiation-curable compounds include acrylic double bonds such as acrylic acid, methacrylic acid, or their ester compounds, which exhibit radically polymerizable unsaturated double bonds, and allylic double bonds such as diallylphthalate. It is a thermoplastic resin containing or introducing into its molecules a group that can be crosslinked or polymerized and dried by radiation irradiation, such as a double bond or an unsaturated bond such as maleic acid or a maleic acid derivative.
Any compound having an unsaturated double bond that undergoes cross-linking polymerization upon irradiation with low radiation can be used.

The following unsaturated polyester resins are examples of resins containing groups in the molecule of thermoplastic resins that can be crosslinked or polymerized and dried by radiation irradiation. □ A polyester compound containing a radiation-curable unsaturated double bond in its molecular chain, such as a saturated polyester resin consisting of an ester bond of a polybasic acid and a polyhydric alcohol as shown in (2) below, in which part of the polybasic acid is converted to maleic acid. Examples include unsaturated polyester resins containing radiation-curable unsaturated double bonds. 'Radiation-curable unsaturated polyester resin is prepared by adding maleic acid, fumaric acid, etc. to at least one polybasic acid component and at least one polyhydric alcohol component, and treating it in the usual manner, that is, in the presence of a catalyst, at 180 to 200°C in a nitrogen atmosphere. After dehydration or dealcoholization reaction, the temperature can be raised to 240 to 280°C, and a condensation reaction can be performed under reduced pressure of 0.5 to 1 mmHH. Maleic acid, fumaric acid, etc., have an acid content of 1 to 40% due to crosslinking during manufacturing, radiation curability, etc.
It is mol%, preferably 10 to 30 mol%.

Examples of thermoplastic resins that can be modified into radiation-curable resins include the following.

(1) Vinyl chloride copolymer Vinyl chloride-vinyl acetate-vinyl alcohol copolymer, vinyl chloride-vinyl alcohol copolymer, vinyl chloride-vinyl alcohol-vinyl propionate copolymer, vinyl chloride-vinyl acetate-malein Acid copolymers, vinyl chloride-vinyl acetate-vinyl alcohol-maleic acid copolymers, vinyl chloride-vinyl acetate-fiOH side chain alkyl group copolymers, such as UCC
VROH, VYNClVYEGX, VERR%VY
ES% VMCA.

VAGH%UCARMAG520, UCARMAG52
a, etc., and radiation sensitivity modification is performed by introducing an acrylic double bond, a maleic acid double bond, or an allylic double bond into this material.

These may contain carboxylic acids.

(2) Saturated polyester resin Saturated polybasic acids such as phthalic acid, isophthalic acid, terephthalic acid, succinic acid, adipic acid, and sebacic acid, and ethylene glycol, diethylene glycol, glycerin, trimethylolpropane, 1,2 propylene glycol,
Esters with polyhydric alcohols such as 1.3-butanediol, dipropylene glycol, 1.4-butanediol, 1.6-hexanediol, pentaerythritol, sorbitol, glycerin, neopentyl glycol, 1.4-cyclohexane dimetatool. Saturated polyester resins obtained by bonding or these polyester resins are
Examples include resins modified with O3Na etc. (for example Vylon 53S), which also undergo radiation sensitivity modification.

(3) Polyvinyl alcohol-based resin Polyvinyl alcohol, butyral resin, acetal resin, formal resin and copolymers of these components,
Radiation sensitivity modification is performed on the hydroxyl groups contained in these resins.

(4) Epoxy resin, phonoxy resin Epoxy resin produced by the reaction of bisphenol A with epichlorohydrin or methyl epichlorohydrin, such as manufactured by Shell Chemical (Epicoat 152.154, 828, 10 old, 1004)
．． 1007), manufactured by Dow Chemical (DEN431, D
ER732, DER51! .

DER331), Dainippon Ink (Evicron 400.
80G), and phenoxy resin manufactured by UCC, which is a high polymerization degree resin of the upper epoxy (HA, PKHC, PK in P)
HH), copolymer of brominated bisphenol A and epichlorohydrin, manufactured by Dainippon Ink and Chemicals (Evicron 1
45.152, 153.1120), etc., and these also include those containing a carboxylic acid group.

Radiation sensitivity modification is performed using the epoxy groups contained in these resins.

(5) Various cellulose derivatives are used, but particularly effective ones include nitrified cotton, cellulose acetobutyrate, ethyl cellulose, butyl cellulose, and acetyl cellulose. Perform sensory degeneration.

Other resins that can be used for radiation sensitivity modification include polyfunctional polyester resins, polyether ester resins, polyvinylpyrrolidone resins, and derivatives (pvp
Also effective are acrylic resins containing at least one of olefin copolymers), polyamide resins, polyimide resins, phenol resins, spiroacetal resins, acrylic esters and methacrylic esters containing hydroxyl groups as polymerization components.

Examples of elastomers or prepolymers are listed below.

(1) The use of polyurethane elastomer or prepolymer polyurethane provides abrasion resistance and the base film,
For example, it is particularly effective in terms of good adhesion to PET film. Examples of urethane compounds include 2,4-toluene diisocyanate, 2,6-
Toluene diisocyanate, 1,3. -xylene diisocyanate, 1.4-xylene diisocyanate, 1.
5-naphthalene diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate, 3.
3'-dimethyl-4,4'-diphenylmethane diisocyanate, 4,4'-diphenylmethane diisocyanate, 3,3'-dimethylbiphenylene diisocyanenite, 4,4'-biphenylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, dicyclohexylmethane Various polyvalent isocyanates such as diisocyanate, desmodur and desmodur N, and linear saturated polyester (ethylene glycol,
Polyhydric alcohols such as diethylene glycol, glycerin, trimethylolpropane, 1,4-butanediol, 1,6-hexanediol, pentaerythritol, sorbitol, neopentyl glycol, 1,4-cyclohexane dimetatool, and phthalic acid. , by condensation polymerization with saturated polybasic acids such as isophthalic acid, terephthalic acid, succinic acid, adipic acid, and sebacic acid), linear saturated polyethers (polyethylene glycol, polypropylene glycol, polytetramethylene glycol) and caprolactam, Polyurethane elastomers and prepolymers made of polycondensates of various polyesters such as hydroxyl-containing acrylic esters and hydroxyl-containing methacrylic esters are effective.

By reacting the terminal isocyanate group or hydroxyl group of these urethane elastomers with a monomer having an acrylic double bond or an allylic double bond,
Modification to radiosensitivity is very effective.
It also includes those containing OH, COOH, etc. as a polar group at the end.

Furthermore, monomers having an unsaturated double bond that have an active hydrogen that reacts with an isocyanate group and are radiation curable, such as long-chain fatty acid or diglycerides that have an unsaturated double bond, are also included.

(2) Acrylonitrile-butadiene copolymer elastomer Elastomers such as an acrylonitrile-butadiene copolymer prepolymer with a terminal hydroxyl group commercially available as PolyBD Retired Resin manufactured by Sinclair Vetro Chemical Co., Ltd. or Hiker 1432J manufactured by Nippon Zeon Co., Ltd. are particularly suitable for butadiene-based elastomers. It is suitable as an elastomer component whose double bonds are crosslinked and polymerized by generating radicals by radiation.

(3) Polybutadiene Elastomer A prepolymer having a low molecular weight terminal hydroxyl group, such as PolyBD Retired Resin R-15 manufactured by Sinclair Vetro Chemical Co., is particularly suitable from the viewpoint of compatibility with thermoplastic resins.
Since the R-15 prepolymer has a hydroxyl group at the molecular end, it is possible to increase the radiation sensitivity by adding an acrylic unsaturated double bond to the molecular end, making it more advantageous as a binder.

In addition, polybutadiene cyclized product, CBR- manufactured by Japan Synthetic Rubber Co., Ltd.
M901 also has excellent properties when combined with thermoplastic resin.

Other suitable thermoplastic elastomer and prepolymer systems include styrene-butadiene rubber, chlorinated rubber, acrylic rubber, isoprene rubber, and its cyclized product (ClR701 manufactured by Nippon Synthetic Rubber), epoxy-modified rubber, internal plastic Elastomers such as saturated linear polyester (Toyobo Vylon #300) can also be effectively used by subjecting them to radiation-sensitive modification treatment.

Compounds having radiation-curable unsaturated double bonds used as oligomers in the present invention include styrene, ethyl acrylate, ethylene glycol diacrylate, ethylene glycol dimethacrylate, diethylene glycol diacrylate, diethylene glycol dimethacrylate, 1. 6-hexane glycol diacrylate, 1,6-hexane glycol diacrylate, N-vinylpyrrolidone, pentaerythritol tetraacrylate (methacrylate), pentaerythritol triacrylate (methacrylate), trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, polyester Functional oligoester acrylate (Aronix M-7100, M-5400, 55
00, 5700, etc., Toagosei), urethane elastomers with acrylic modified products of Kpponran 4040), or those into which functional groups such as C0OH have been introduced, trimethylolpropane diacrylate (methacrylate) phenol ethyleneoxide adducts. Acrylate (methacrylate), a compound with an acrylic group (methacrylic group) or ε-caprolactone-acrylic group attached to a pentaerythritol condensed ring represented by the following general formula, where m = 1, a = 2, b = 4 (hereinafter referred to as special pentaerythritol condensate A), m = 1, a = 3, b = 3 compound (hereinafter referred to as special pentaerythritol condensate B), m = 1, a = 6, b =
o compound (hereinafter referred to as special pentaerythritol condensate C
), m = 2, a = 6, b = o (hereinafter referred to as special pentaerythritol condensate), and special acrylates represented by the general formula below.

1) (CH2=CHCOOCH2)3-CCH20
H (special acrylate A) 2) (C)12 =CHCOOCH2)3-CC
H20H3 (special acrylate B) 3) (CH2=CHC0(OC3H6)n -0
CH2) 3-CCH2CH3 (Special acrylate C) (Special acrylate D) (Special acrylate E) (Special acrylate F) (16 out of n) (Special acrylate G) 8)
CH2=CHCOO-(CH2CH20)4-CO
CH=CH2 (Special acrylate H) (Special acrylate ■) (Special acrylate J) A Niacrylic acid, X: Polyhydric alcohol Y: Polybasic acid (Special acrylate K) 12) A+M
-N÷-M-A A Niacrylic acid, M: Dihydric alcohol N: Dibasic acid (Special acrylate) It is known that some polymers disintegrate when irradiated with radiation, while others cause cross-linking between molecules. .

Examples of substances that cause crosslinking between molecules include polyethylene, polypropylene, polystyrene, polyacrylic ester,
polyacrylamide, polyvinyl chloride, polyester,
There are polyvinylpyrrolidone rubber, polyvinyl alcohol, and polyacrylene. If such a crosslinked polymer is used, the crosslinking reaction will occur even without the above-mentioned modification, so these resins can be used as they are in addition to the above-mentioned modified products.

- In order to cure such a radiation-curable resin, various known methods may be used.

Note that when ultraviolet rays are used for curing, a photopolymerization sensitizer is added to the radiation-curable compound as described above.

The photopolymerization sensitizer may be a conventionally known one, such as benzoin type sensitizers such as benzoin methyl ether, benzoin ethyl ether, α-methylbenzoin, α-chlordeoxybenzoin, benzophenone, acetophenone, bisdialkylaminobenzophenone, etc. Examples include ketones, quinones such as acedraquinone and phenanthraquinone, and sulfides such as benzyl disulfide and tetramethylthiuram monosulfide.

The photopolymerization sensitizer is desirably in a range of 0.1 to 10% by weight based on the solid content of the resin.

For ultraviolet irradiation, for example, an ultraviolet light bulb such as a xenon discharge tube or a hydrogen discharge tube may be used.

On the other hand, when using an electron beam, the radiation characteristics are as follows:
Accelerating voltage 100-750KV, preferably 150-30KV
Using a 0KV radiation accelerator, the absorbed dose is 0.5-20
It is convenient to irradiate in a megadose manner.

In particular, as an irradiation source, the method of using an electron beam using a radiation heater and the method of using ultraviolet rays described above are advantageous from the viewpoint of controlling the absorbed dose, introducing into the manufacturing process line, shielding ionizing radiation, etc. .

Furthermore, according to this method, even a solvent-free resin that does not use a solvent can be cured in a short time, so such a resin can be used.

By using such a radiation-curable resin, large diameter so-called jumbo rolls are free from tight winding, and the difference in electromagnetic conversion characteristics between the inside and outside of the jumbo rolls is eliminated and the characteristics are improved. Also, since it can be done online, productivity is improved.

The weight ratio of magnetic powder/binder is preferably 1/1 to 9/1, particularly i/1 to 8/1.

The reason for using such a ratio is that if it is less than 1/1, the saturation magnetic flux density will be low, and if it exceeds 9/1, the surface roughness will deteriorate due to poor dispersion, and the coating film will become brittle, which is not desirable.

In the present invention, a non-reactive solvent is used if necessary.
There are no particular restrictions on the solvent, but it is appropriately selected in consideration of the solubility and compatibility of the binder.

For example, ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone, esters such as ethyl formate, ethyl acetate, and butyl acetate, alcohols such as methanol, ethanol, isopropanol, butanol, and aromas such as toluene, xylene, and ethylbenzene. group hydrocarbons, ethers such as isopropyl ether, ethyl ether, dioxane, tetrahydrofuran,
Furfural and other furans are used as a single solvent or a mixture of these solvents.

These solvents are 10 to 10,000w to the binder.
It is used at a ratio of t%, especially 100 to 5000 wL%.

The magnetic layer may contain an inorganic pigment.

Inorganic pigments include 1) conductive carbon black, graphite, and graphitized carbon black, and 2) inorganic fillers such as 5i02, TiO2, and AIt.
203, Cr2O3, S i C%Cab%CaCO
3. Zinc oxide, goethite, γ-Fe2O3, talc,
Examples include kaolin, CaSO4, boron nitride, graphite fluoride, molybdenum disulfide, and ZnS. In addition, the following fine particle pigments (aerosil type, colloidal type)
:5i02, Al2O3, TiO2, 2r02, Cr203, Y203, CeO2, Fe304,
Fe203, ZrSiO4, Sb205.5n02, etc. are also used. These fine particle pigments are, for example, 5i02
In the case of ■Ultrafine particle colloidal solution of silicic anhydride (Snowtex, water-based, methanol silica sol, etc., 0-san chemical),
■Ultrafine particulate anhydrous silica (!YA quasi-product 100 people) (Aerosil, Nippon Aerosil Co., Ltd.) manufactured by combustion of purified silicon tetrachloride is included. Further, the ultrafine particle colloidal solution of (1) above, ultrafine aluminum oxide produced by the same vapor phase method as (2), titanium oxide, and the above-mentioned fine particle pigment may be used. Regarding the usage amount of such inorganic pigments, binder 100
1 to 30 parts by weight, and 1 for 2)
-30 parts by weight is suitable; if the amount is too large, the coating film becomes brittle and dropouts tend to increase.

Regarding the diameter of the inorganic pigment, 1) is 0.1μ.
- or less, more preferably 0.05 μm or less, and regarding 2), 0.7 μm or less, further preferably 0.5 μm or less.

The magnetic layer may contain a dispersant.

Organic titanium coupling agents, silane coupling agents and surfactants are used as dispersants, natural surfactants such as saponin are used as antistatic agents: nonionic surfactants such as alkylene oxide, glycerin, and glycidol: higher alkyl amines. cationic surfactants, such as quaternary ammonium salts, pyridine and other heterocycles, phosphonium or sulfonium; anionic surfactants containing acidic groups such as carboxylic acid, sulfonic acid, phosphoric acid, sulfuric acid ester groups, and phosphoric acid ester groups; Ampholytic active agents such as amino acids, amino sulfonic acids, sulfuric acid or phosphoric acid esters of amino alcohols, and the like are used.

The magnetic layer may contain a lubricant.

As the lubricant, silicone oil, fluorine oil, fatty acid, fatty acid ester, paraffin, liquid paraffin, surfactant, etc. can be used as the lubricant conventionally used in this type of magnetic recording medium, but fatty acid and/or Preferably, fatty acid esters are used.

Examples of fatty acids include fatty acids with 12 or more carbon atoms (RCO
OHlR is an alkyl group having 11 or more carbon atoms), and fatty acid esters include fatty acid esters consisting of a monobasic fatty acid having 12 to 16 carbon atoms and a monohydric alcohol having 3 to 12 carbon atoms, and 17 carbon atoms. A fatty acid ester consisting of a monobasic fatty acid of 1 or more and a monohydric alcohol having 21 to 23 carbon atoms in total, and an alkali metal or alkaline earth of the fatty acid is used. Metal soaps made of metal, lecithin, etc. are used.

As the silicone, those made of fatty acid-modified silicones and those partially fluorine-modified are used. The alcohol used is one made of higher alcohol, and the fluorine used is one obtained by electrolytic substitution, telomerization, oligomerization, etc.

Among the lubricants, it is also advantageous to use radiation-curable types. These products suppress the transfer of the back die to the back surface, preventing dropouts, reducing output differences depending on the inner and outer diameters when wound into a roll, and have other advantages such as being able to be manufactured online. have

Radiation-curable lubricants include compounds that have a molecular chain exhibiting lubricity and an acrylic double bond in their molecules, such as acrylic esters, methacrylic esters, vinyl acetate esters, acrylic amide compounds, and vinyl alcohol esters. , methyl vinyl alcohol ester, allyl alcohol ester, glyceride, etc. The structural formula of these lubricants is CH2=CH-CH2C0OR.

CH2=CHC0NHCH2C0OR.

RCOOCH=CH2, RCOOCH2-CH=CH2, etc., where R is a linear or branched saturated or unsaturated hydrocarbon group, and the number of carbon atoms is 7 or more, preferably 12 or more and 23 or less, and these are fluorine It can also be a substituted product.

As a fluorine substituted product, CnF −1Cn F 2n+1(CI(2) m
-2n+ 1 (however, m=1 to 5), CnFnC)12C82NHC)(2CH2-1Cn
There are COOCR2C112-n-1, etc.

Preferred specific examples of these radiation-curing lubricants include:
Examples include stearic acid methacrylate (acrylate), stearyl alcohol methacrylate (acrylate), glycerin methacrylate (acrylate), glycol methacrylate (acrylate), and silicone methacrylate (acrylate).

The dispersant and lubricant are 0.1 to 20% relative to the binder.
Parts by weight may be included.

(2) Specific effects of the invention According to the invention, barium ferrite powder is obtained by mixing two or more metal acetylacetones including Ba acetylacetone and Fe acetylacetone as starting materials and hydrolyzing the mixture.

The barium ferrite powder thus obtained has extremely excellent magnetic properties.

Furthermore, a magnetic recording medium using such barium ferrite powder has extremely excellent medium characteristics.

(2) Specific Examples of the Invention Hereinafter, specific examples of the present invention will be shown and the present invention will be explained in more detail.

[Example 1] Ba (C5H702)2 4H20 and Fe (
C5H702)3 was blended so that the final composition was BaO(Fe203), which is M-phase Ba ferrite, at 6°, 700 CC of ethanol was added thereto, and the mixture was heated to reflux at the boiling point of ethanol. After heating under reflux for 1 hour, the mixture was cooled as it was, and about 24 hours later, 200 cc of aqueous ammonia was added at room temperature. After aging for 2 days, a heating reaction was carried out at 80° C. for 3 hours to complete the hydrolysis.

Thereafter, the precipitate precipitated in the solvent by hydrolysis was filtered off by suction filtration and dried.

Then, what solidified during drying was loosened into powder and fired in the air to make a fired sample. The firing temperature was 900°C. The firing time was 1 hour.

The crystallization of the ferrite powder was confirmed by X-ray diffraction. The results of X-ray diffraction are shown in FIG. From the results shown in FIG. 1, it was found that it was a single M phase. The magnetic properties of sample 1 of the present invention obtained in this way are σ5
=62,'7 eIIlu/g, or=35.1
emu/g.

1Hc=60000e. Also, the average particle size is 60
There were 0 patients, and the platy ratio was 3.

Furthermore, for comparison of magnetic properties, the following comparative sample 11
~13 were produced.

(Preparation of Comparative Sample 11) Ba (OC2H5)2 and Fe (C5H2O2)3 were blended so that the final composition was BaFe12O19, ethanol was added thereto, and after refluxing at about 70°C for 1 hour in a nitrogen stream, the following Aqueous ammonia was added thereto and aged for 1 hour to form a precipitate to obtain a fine powder, which was then heat treated at 900° C. to produce Comparative Sample 11. When we measured the magnetic properties of this product, we found that σ5=62.2
eIIlu/g%or=33-34 emu/g%1H
c=5,000 0e, average particle size of 1,000 particles, and plate ratio of 2.

(Preparation of comparative sample 12) Ba (OC2Hll)2 and Fe (C3H.

O) was blended so that the final composition was BaFe12O19, and Comparative Sample 12 was produced according to the manufacturing method of Comparative Sample 11 above.

The magnetic properties of this material are σs=57emu/g, cyr=
30 emu 7 g, 1 l (c = 5000 0e. The average particle size was 1200, and the platelet ratio was 1.5.

(Production of Comparative Sample 13) Comparative Sample 13 was produced according to the method for producing Comparative Sample 11 above using Ba (OC2H&) and Fe (OC285)3.

The magnetic properties of this material are σS = 63, Oemu/
g, or=31emu 7g,i Hc=48000e
Met. Particle size is average particle diameter 900λ, plate ratio 1
．． It was 8.

[Example 2] In Example 1, an experiment was conducted by changing the firing temperature to 850 to 1250°C.

The ratio of BaFe+20tg phase (M phase) and αFe2O3 phase was measured by X-ray diffraction, and the ratio of iHc, as,
or was measured.

From these results, it was confirmed that M phase with good magnetic properties was generated at 850 to 1050°C.

[Example 3] In Example 1, a sample was prepared by firing at a firing temperature of 1300° C. for 5 hours at an atmospheric pressure of PO2/(PO2+PN2)=10-3.

When X-ray diffraction was performed on this material, a single W phase was found.
Formation of phases was confirmed. The magnetic properties of this sample are C
s = 70 emu/g, i Hc = 200
It was 0e.

[Example 4] The final composition is M-layer Ba ferrite in which -0 parts of Ba and Fe are replaced with Co and Ti, that is, BaFe+2-2x
Ba (C.) so that Go, Tix 019 (X=0.85).

Ht 02) 2” 4H20, FfB
(C6HtQ2)3, Co(C5
Ht Ox )z ・2H20, TiO(Cs
A substituted Ba ferrite powder was prepared in the same manner as in Example 1 by blending Ht 02)2.

X-ray diffraction was performed in the same manner as in Example 1. The results are shown in Figure 2. From the results shown in FIG. 2, it is confirmed that it is a single-phase M layer.

The magnetic properties of Sample 5 of the present invention thus obtained are: o s = 57 emu/g, or = 25
emu/g %i Hc = 8000 e.

Further, the particle size was an average particle size of 500 particles and a plate-like ratio of 3.

In addition, in Comparative Sample 11, a part of Ba and Fe was replaced with Co using an alkoxide at the same composition ratio as Sample 5.
, and those substituted with Ti were prepared (comparative sample 15).

These particle sizes were made to be equivalent to Sample 1 of the present invention.

Regarding the characteristics of comparative sample 15, σS=50 em
u/g, Or = 20 etau/g%i
Hc = 700 0e.

(Example 5) A magnetic paint was prepared using the barium ferrite of the present invention sample 5 prepared in Example 4 as follows.

Barium ferrite 120 parts by weight (Hc=80
0) α-An2o3 (0.5 μm powder) 2 parts by weight Carbon black (20 m μm) 10 parts by weight Solvent (ME/toluene: 50150) 100 parts by weight The above composition was mixed in a ball mill for 3 hours, and barium Wet the ferrite well.

Next, as a binder, vinyl chloride-vinyl acetate-vinyl alcohol copolymer (
Maleic acid content: MW40,000) 6 parts by weight (solid content equivalent)
, Acrylic double bond-introduced vinyl chloride-vinyl acetate-vinyl alcohol copolymer (contains maleic acid; MW20,000) 12 parts by weight (calculated as solid content)
, 9 parts by weight of acrylic double bond-introduced polyether urethane elastomer (MW 40,000) (calculated as solid content), 3 parts by weight of pentaerythritol triacrylate, 200 parts by weight of solvent (ME/toluene; SO/5O), 4 parts by weight of stearic acid. parts by weight, and 2 parts by weight of butyl stearate were mixed and dissolved.

This was placed in a ball mill containing a barium ferrite (hereinafter referred to as magnetic powder) mixture and was again partially dispersed for 42 hours.

The magnetic paint thus obtained was used as a raw material for the magnetic layer of the medium, and a magnetic recording medium was manufactured by the steps shown below.

A 75 μm thick polyester (PET) film was used as a support, and the transport speed was 100 m/min.

A coating film was applied by gravure coating, and then the magnetic powder in the magnetic layer was oriented by being continuously conveyed into an orientation device. As a magnetic field! A pair of N-S opposing magnets was used, the gap between the opposing magnetic poles was 15 mm, and the length of the magnetic poles was 800 mm.

The magnet used had a central magnetic field of 3000G.

The orientation device is installed inside the drying oven, and inside the drying oven,
Hot air was continuously sent, and the paint film was dried to some extent while being oriented by the magnetic field, thereby preventing the effects of the demagnetizing field. The temperature of the hot air was 90°C, and the air volume was about 50cm37m1n.

Thereafter, in order to roughly improve the degree of vertical orientation and surface roughness, it was passed through 10 calender rolls with a diameter of 10 cm. Note that the linear pressure by the calender roll was approximately 100 g, and the calender rolling rate was 1/20.

In this way, the vertical alignment and surface smoothing are completely completed, and then the material is passed through a radiation irradiation device.
The binder was allowed to fully cure and was rolled up using a take-up roll to create a sample of the media. The absorbed dose of radiation was set at 5 megarads.

This was designated as medium A.

According to this, medium B was also produced using the barium ferrite of comparative sample 15 of Example 4.

For further comparison, Fe2O3,Coo, Tie, ,
Each raw material of B2O3 is melted in a platinum crucible at 1300℃ or above, then rolled and rapidly cooled using a twin roll method, and the resulting glass is heated to 60℃.
0 was reheated at above temperature to crystallize Ba ferrite.

Comparative sample 20 was obtained by dissolving the matrix and extracting Ba ferrite particles.

The composition is B a Fe-+o, 3COo, asT j
o, aso I@, and Hc=8000e1 σs
=55 emu/g.

Comparative medium C was produced in the same manner as medium A using this comparative sample 20.

The following characteristics of these media A to C were investigated.

(1) Measured tape relative speed at 5 MHz playback output: 3.75 m/s Magnetic head: Sender string head (gab: 0.2
8#m, track width: 264) (2) Signal-to-noise ratio (C
Table 1 shows the ratio C/N results between the 5 MHz carrier output C (rms) and the medium noise N (rms) obtained by subtracting the device noise from the 4 MHz modulation noise.

Table 1 Medium Barium Signal vs. Regenerated Ferrite No., Sample No., Noise Ratio Output A
This invention 55dB 155μVp-
p sample 5 B (comparison) comparison 45dB 140 μV
pp sample 15 C (comparison) comparison 50dB 150 μV
pp sample 20 The effects of the present invention are clear from the above results.

That is, it can be seen that the medium using the powder of the present invention is superior in reproduction output and signal-to-noise ratio compared to the medium using powder produced by the conventional vitrification crystal method and alkoxide method.

[Brief explanation of the drawing]

FIGS. 1 and 2 are X-ray diffraction charts of samples of the present invention, respectively. FIG, 1 = Ding

Claims (2)

[Claims] (1) A ferrite powder characterized in that two or more metal acetylacetones including Ba acetylacetone and Fe acetylacetone are mixed, hydrolyzed, and then calcined. (2) Two or more metal acetylacetones including Ba acetylacetone and Fe acetylacetone are mixed, hydrolyzed, and then fired to obtain M-phase ferrite powder, and a magnetic paint containing this M-phase ferrite powder and a binder. 1. A magnetic recording medium comprising: coated on a non-magnetic support.