JPH02138708A - Hexagonal system ferrite magnetic powder and magnetic recording medium - Google Patents

Abstract

PURPOSE:To prevent the deterioration of a solvent medium when a magnetic coating material is manufactured by a method wherein the physical properties of surface of powder is remodelled by conducting a prescribed surface treatment on hexagonal system ferrite magnetic powder. CONSTITUTION:Hexagonal system ferrite magnetic powder is surface-treated using tangstic acid anion and/or molybdic acid anion. WO4<2->, [W12O46]<20->, and the like, MoO4<2->, [MoO7O24]<6-> and the like are used. The larger the valence number becomes, the easier the specific attraction becomes. Magnetic powder is dispersed into the aqueous solution of tangstate or molybdate and anion is adsorbed. The surface density of the tangstic acid ions on the magnetic powder is selected to 0.1 to 10ion/nm<2>, and the surface density of molybdic acid ion is also selected in the range same as above- mentioned. This surface-treated magnetic powder is kneaded with bonding resin, and it is spread on the surface of the non-magnetic supporting member which is publicly known. According to this constitution, no deterioration is generated in a solvent medium when it is formed into a coating material, high filling adaptability and a high orientation can be obtained, and a recording medium of high output can also be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention provides a coating-type vertical '6ff recording medium that achieves high-density recording.
The present invention relates to a hexagonal ferrite magnetic powder used as a 6n powder for magnetic recording media.

Furthermore, the present invention provides a coating-type vertical six
The present invention relates to magnetic recording media such as R-air recording media, and particularly relates to I-air recording aphrodisiacs containing the hexagonal ferrite magnetic powder subjected to a predetermined surface treatment in a 6n layer.

[Summary of the invention]

The present invention provides hexagonal ferrite (Hn) powder by performing predetermined surface treatment on hexagonal ferrite Hn powder.
The objective is to improve the surface properties of the R-type powder, and to provide, for example, an Iff-type powder (hexagonal ferrite that can prevent deterioration of the solvent when prepared into an R-type paint).

Furthermore, the present invention allows the magnetic layer to contain hexagonal ferrite magnetic powder that has been subjected to a predetermined surface treatment, thereby achieving high filling and orientation of the magnetic powder, thereby making it possible to achieve high output. The purpose is to provide a magnetic recording medium.

[Conventional technology]

For magnetic recording media used in perpendicular magnetic recording type recording and reproducing devices, a magnetic layer is formed by directly depositing a metal material such as Co-Cr on a non-magnetic support by vacuum evaporation or sputtering. There is active research into magnetic recording media of the so-called metal W model. However, this metal 7filfI'J type magnetic recording medium still has practical problems in terms of running durability and production efficiency, and for this reason, coating-type perpendicular magnetic recording media that can be manufactured by a coating method are being considered. has been done.

For example, 60,000 fried rice)! The coating-type magnetic recording medium using 51 magnetic powder uses conventional needle-shaped magnetic powder (unlike the B magnetic recording medium, it is expected to be used as a magnetic recording medium for short wavelength recording and perpendicular magnetic recording. There is.

A magnetic recording medium using the above-mentioned hexagonal ferrite Tll powder can be manufactured by the same method as a conventional coating type magnetic recording medium, for example, by combining the above-mentioned hexagonal ferrite magnetic powder, a resin binder, and a solvent. It is created by preparing a magnetic coating material, coating it on a non-magnetic support, and drying it.

In this case, the poor dispersibility of the 6ff type ferrite powder has traditionally been considered a problem;
Publication No. 4 discloses that 5i(h) is attached to the surface of hexagonal oxide particles to improve the dispersibility.

[Problem to be solved by the invention]

By the way, when preparing the above-mentioned hexagonal ferrite m-type powder into a magnetic coating material, not only the dispersibility but also the surface physical properties are important factors. Solvent and hexagonal ferrite I
Interaction with -+fi powder becomes a problem. For example, ketone solvents (acetone, methyl ethyl ketone, methyl isobutyl ketone, nclohexanone, etc.), which are good solvents for resin binders, are widely used as solvents for preparing magnetic paints, but hexagonal ferrite l- When Ml powder was used as magnetic powder, it was found that the solvent deteriorated and that there were residual components even after drying the magnetic layer.

However, conventional studies have mainly focused on dispersibility as described above, and the actual situation is that the surface properties of hexagonal ferrite Eff powders, which cause such deterioration of solvents, have hardly been elucidated.

On the other hand, in a perpendicular magnetic recording medium formed by coating a non-magnetic support on a non-magnetic support, a hexagonal ferrite n-type powder containing the above-mentioned problems is used as a magnetic powder.
In the C3I layer, the filling rate of the hexagonal ferrite powder is not very high, and furthermore, even if orientation treatment is performed, sufficient orientation cannot be obtained. Currently, in recording media, it is not possible to sufficiently increase the output of magnetic recording media.

The present invention was proposed in view of the above-mentioned circumstances, and aims to provide a hexagonal ferrite powder with improved surface properties and less interaction with solvents. It is something.

Furthermore, the present invention uses a hexagonal ferrite magnetic powder with improved surface properties and less interaction with solvents, thereby increasing the filling of the magnetic powder.

The object of the present invention is to provide a magnetic recording medium that is highly oriented and capable of achieving high output.

[Means to solve the problem]

In order to achieve the above-mentioned objective, the present inventors conducted intensive research and found that the surface of hexagonal ferrite magnetic powder acts as a basic heterogeneous catalyst and generates a polymeric compound that behaves as a residual solvent. Heading: Hexagonal ferrite 611, which has less interaction with solvents, is produced by performing a predetermined surface treatment on the above-mentioned hexagonal ferrite +-1 powder.
We have come to the knowledge that it is possible to provide a sex powder.

In addition, hexagonal ferrite with the above-mentioned surface treatment)
By using the Tff type powder as the magnetic powder of the perpendicular magnetic recording medium, the dispersibility of the hexagonal ferrite type powder in the magnetic coating material is improved, and high filling properties in the magnetic layer are achieved.
We have come to the conclusion that high orientation can be achieved.

The hexagonal crystalline powder of the present invention has been completed based on such knowledge, and is characterized by being surface-treated with tungstate anions and/or molybdate anions.

Furthermore, the magnetic recording medium of the present invention is a magnetic recording medium comprising a magnetic layer containing a magnetic powder and a binder resin on a non-magnetic support, wherein the magnetic powder is an anion of tungstate and/or an anion of molybdate. It is characterized by containing a hexagonal crystal ferrite surface-treated with 411 powder.

The hexagonal ferrite magnetic powder to which the present invention is applied has the general formula MO・n(FezOt)C, where M is Ba,
Sr.

It represents at least one type of Ca, and n=5 to 6. ] It is mainly composed of fine particles of hexagonal ferrite. In this case, in order to control the coercive force, Co, TI, Ni, Mn+Cu, Zn, In+G
At least one of e+Nb may be added to replace a part of Fe in the hexagonal ferrite with these elements. For example, in Ba ferrite where M is Ba, when part of Fe is replaced by the above element, its composition has the general formula Ba0-n(Fe+-J+a)zOs (however,
In the formula, X is Co, Ti, Ni, gate n, Cu, Zn, In
, Ge, and Nb, and m is 0 to 0.
．． 2, n is 5-6. ] Represented by .

There are no particular restrictions on the particle size, but it is usually 0.02
It is about 0.50 μm.

Further, methods for producing the above-mentioned hexagonal ferrite fine particles include, for example, a flux method, a glass crystallization method, a hydrothermal synthesis method, a coprecipitation method, etc., but are of course not limited to these methods, and are conventionally used. Any known method may be used.

In the present invention, the surface of a magnetic powder represented by the above-mentioned hexagonal ferrite is treated with tungstate anions and/or molybdate anions.

The above-mentioned tungstate anion used for surface treatment of magnetic powder includes orthotungstate ion ("
), paratungstate ion (W+zLi) ”-
(W+zLJ+.) 1G-, metatungstate ion (IblLx04゜]] S-1 pseudo-methatungstate ion W40zi '-, etc. Also, molybdate anions include orthomolybdate ion (
Mo04”-), paramolybdate ion (MotO
zs) '\Metamolybdate ion (Mo60□6)
4- etc. are mentioned. When treating with these tungstate anions and/or molybdate anions, the higher the valence, the easier it is to cause specific adsorption, so it is preferable that the valence is bivalent or higher.

Various methods can be used to adsorb the tungstate anion or molybdate anion onto the surface of the magnetic powder. For example, the tungstate anion can be adsorbed onto the surface of the magnetic powder by dispersing the magnetic powder in various tungstate aqueous solutions or molybdate aqueous solutions. Alternatively, a method of adsorbing molybdate anions, a method of treating with an alkoxy compound of tungsten or molybdenum followed by a dealcoholization treatment, or a method of treating with an organometallic compound of tungsten or molybdenum followed by an oxidation treatment can be considered.

The tungstate aqueous solution or molybdate aqueous solution i
In the method of processing in 8M, the cation constituting the tungstate or molybdate is preferably a -valent cation. Such cations include NII
J"ii', Na", Ni', llb"Cs', etc. Or hydroxides coexisting with H" (for example, Na
llMo0. , NaHWO4, etc.).

These valent cations have low specific adsorption to the magnetic powder surface and can be easily removed after treatment with tungstic acid or molybdic acid.

In the present invention, the adsorbed amount of the tungstate ions is 5 to 0.05 parts by weight, preferably 2 to 0.05 parts by weight in terms of tungsten metal weight, per 100 parts by weight of the magnetic powder.
It is 1 part by weight. In addition, the surface density of tungstate ions on the magnetic powder is 50 to 0.05 ions/nl112,
Preferably it is to~0.1 ion/nm2.

On the other hand, the amount of molybdate ion adsorbed is 1 part by weight of molybdenum metal per 100 parts by weight of magnetic powder.
The amount is 0 to 0.01 part by weight, preferably 5 to 0.05 part by weight. In addition, the surface density of molybdate ions on the magnetic powder is 50 to 0.05 ions/r+m"-, preferably l
O~0.1 ion/nmz.

If the amount of tungstate anion or molybdate anion is too small outside this range, the desired effect will not be obtained, and conversely, if it is too large outside this range, the magnetization per unit amount of magnetic powder will decrease. Undesirable.

The above-described ion adsorption treatment can be performed in an aqueous system, and can be performed using an aqueous solution of the salt of tungstate ion or an aqueous solution of the salt of molybdate ion.

The salt is preferably a monovalent cation with low specific adsorption of a counter cation, such as ammonium salt, lithium salt, sodium salt, potassium salt, etc.

Furthermore, the tungstate anion or molybdate anion used in the surface treatment of the magnetic powder in the present invention can also be used as a composite anion with other oxoacid anions.

Examples of the other oxoacid anions include orthosilicate ions (S+On'-) + metasilicate ions (Sin
, "Metatrisilicate ion (SiJs"-) + Metatrisilicate ion (S + zOs'-) + Metatetrasilicate ion (S
i40□b-), silicate anions such as other polysilicate ions, borate ions such as orthoborate ions, diborate ions, tetraborate ions 1 and other polyborate ions, orthophosphate ions 3 pyrophosphate ions 3 stannate ions such as phosphate ions, other polyphosphate ions, orthostannate ions, metastannate ions, stanrite ions, and other polystannate ions, sulfuric acid (Sod'-)
, sulfate ions such as sulfite (So, 2-), vanadate and other polyvanadate ions, and the like. Furthermore, for tungstate anion, orthomolybdate ion (MOO4”-), paramolybdate ion (
MOt(h4) A-, metamolybdate ion [Mo
110□6)4- etc., and for molybdate anion, orthotungstate ion (wo42-
), paratungstate ion [W+gO44)”
-(W+zOaill+.) 10-, metatungstate ion (HEW, □04°]]5-1 precipitated metatungstate ion WbO+) 3-, and the like.

Furthermore, during the salt aqueous solution treatment, it is preferable to add an acid to the dispersion system in order to improve the adsorption rate of the ions mentioned above. Examples of acids that can be added to the above dispersion include llN0. .

IIc 7! , HBr, IIl, IIc j!
Acids with monovalent acid residue anions such as 0fflIIC10a are preferred. The reason why -valent acids are preferable is that they have low specific adsorption to the surface of magnetic powder. In addition, when the above-mentioned acid is added, it is preferable that the pl+ of the dispersion system is 8 or less, preferably p116.

The adsorption treatment with the tungstate anion or molybdate anion can be carried out by dispersing the ifi powder in an aqueous salt solution, but preferably the unused counter cation after the adsorption treatment or the acid residue used in pHil It is preferable to perform a washing and purification treatment for the purpose of removing the base anion. Furthermore, the washing and purification treatment is performed on p) 18.
Hereinafter, it is possible to reduce desorption of tungstate ions or molybdate ions once adsorbed by preferably using water with p116 or less or a system mainly composed of water.

The magnetic recording medium of the present invention is provided with a magnetic layer containing magnetic powder obtained by the above-described treatment and a binder resin.

Here, the perpendicular magnetic recording medium to which the present invention is applied is produced by applying a magnetic paint made of hexagonal ferrite magnetic powder and binder resin that has been subjected to the above-described predetermined surface treatment to the surface of a non-magnetic support. A tit coating film is formed as a magnetic layer.

In the coating-type perpendicular magnetic recording medium, any conventionally known resin binder and the like constituting the nonmagnetic support and magnetic coating can be used, and there are no limitations in any way.

For example, examples of non-magnetic supports include polymer supports formed from polymer materials such as polyesters, polyolefins, cellulose derivatives, vinyl resins, polyimides, polyamides, polycarbonates, etc. , metal substrates made of aluminum alloys, titanium alloys, etc., ceramic substrates made of alumina glass, etc.
Such as a glass substrate. Its shape is not limited in any way, and it may be in any form such as a tape, sheet, or drum shape. Further, this nonmagnetic support may be subjected to a surface treatment to form fine irregularities in order to control its surface properties.

Examples of resin binders include polymers such as vinyl chloride, vinyl acetate, vinyl alcohol, vinylidene chloride, acrylic esters, methacrylic esters, styrene, butadiene, acrylonitrile, copolymers of two or more of these, and polyurethane resins. , polyester resin, epoxy resin, etc. Hydrophilic functional groups such as carboxylic acid groups, carboxyl groups, and phosphoric acid groups may be introduced into these binders in order to improve the dispersibility of the magnetic powder.

In addition to the resin binder described above, additives such as a dispersant, an abrasive, an antistatic agent, and a rust preventive may be added to the magnetic coating film.

As a method for retaining a lubricant in such a coating type magnetic recording medium, as shown in FIG.
A method in which the lubricant is added internally to the magnetic layer (2) formed as a magnetic coating film thereon, a method in which a lubricant layer (3) is top-coated on the surface of the magnetic layer (2) as shown in FIG. There are methods such as a combination of both.

When applying the above-mentioned lubricant as a top coat, the method of application is to dissolve the lubricant in a solvent and apply or spray the resulting solution, or conversely, to immerse the magnetic recording medium in this solution. All you have to do is cleanse yourself. In this case, the amount of lubricant applied is preferably 0.5 to 100 fflr/m, more preferably 1 to 20 mg/rr+.

The above-mentioned lubricants may be used alone as lubricants for magnetic recording media, but they may also be used in combination with conventionally known lubricants. Alternatively, perfluoroalkyl carboxylic acid ester, carboxylic acid perfluoroalkyl ester,
It can also be used in combination with perfluoroalkylcarboxylic acid perfluoroalkyl esters or derivatives thereof.

Furthermore, in order to cope with more severe conditions and maintain a lubricating effect, an extreme pressure agent may be used in combination at a weight ratio of about 30:10 to 70:30.

The extreme pressure agent reacts with the metal surface due to the accompanying frictional heat when it makes partial metal contact in the boundary lubrication region,
It has a friction and wear prevention effect by forming a reaction product film, and includes phosphorus-based extreme pressure agents, sulfur-based extreme pressure agents, halogen-based extreme pressure agents, organometallic extreme pressure agents, and composite extreme pressure agents. Any of the following agents can be used.

Moreover, in addition to the above-mentioned lubricants and extreme pressure agents, a rust preventive agent may be used in combination, if necessary.

As the rust preventive agent, any of those normally used as a rust preventive agent for this type of magnetic recording medium can be used, such as phenols, naphthols, quinones, heterocyclic compounds containing nitrogen atoms, and oxygen atoms. , a heterocyclic compound containing a sulfur atom, etc.

The rust preventive agent may be used in combination with a lubricant, but as shown in FIG. After applying (4),
It is highly effective to apply the lubricant layer (3) in two or more layers.

Incidentally, in the above-mentioned C11 type recording medium, in addition to the magnetic coating film that is the magnetic layer, a back coat layer, an undercoat layer, etc. may be formed as necessary. For example, the back coat layer is formed by applying the same resin binder as the magnetic coating film to which carbon-based fine powder for imparting conductivity and inorganic pigment for controlling surface roughness are added.

[Effect]

The ferrite type powder used in the present invention is thought to have metal ions exposed on its surface that roughly correspond to the composition.In this case, metal ions with low electronegativity such as Ba'Co2 The metal ion makes the hydroxyl group derived from chemisorbed water bonded to it basic.

Therefore, it is presumed that the surface of this hexagonal ferrite magnetic powder acts as a basic heterogeneous catalyst, polymerizing ketones through the mechanism of aldol condensation, and producing a compound with a higher molecular weight than the catalyst.

These solvents polymerized by condensation are difficult to evaporate during the coating and drying steps of the magnetic coating 4, and behave as residual solvents in the magnetic coating film.

In the present invention, the surface of the hexagonal ferrite Eil powder is treated with tungstate anion or molybdate anion to make it acidic, thereby eliminating its action as a basic heterogeneous catalyst, reducing the aldol condensation activity, and producing ketones. Prevents condensation.

In this case, polyvalent anions in particular have good adsorption to magnetic powder and are difficult to desorb (which is convenient).

A magnetic recording medium containing hexagonal ferrite IF powder, which has excellent dispersibility due to the above-mentioned action, in the magnetic layer,
Highly packed and highly oriented magnetic powder can be achieved, and high output can be achieved.

〔Example〕

Hereinafter, the present invention will be explained using specific examples, but it goes without saying that the present invention is not limited to these examples.

First, an example in which hexagonal ferrite magnetic powder was surface-treated with tungstate anion or molybdate anion will be described.

The hexagonal ferrite magnetic powder used in this example had the following compositions: aFe, o, 1acOo.
, 82Tio, szo+q, and the coercive force 11c is 855 (Oe) and the saturation magnetization σ is 58.0 (e
mu/g), and the specific surface area is 22.1 m''7g.

Disperse 10 parts by weight of 10 parts by weight of hexagonal ferrite) in 100 parts by weight of ion-exchanged water, and further disperse 0.27 parts by weight of sodium orthotungstate (Na2WOa・2+1,0
) was added and subjected to ultrasonic dispersion to adsorb tungstate anions.

Thereafter, this dispersion system was allowed to stand, the supernatant was removed, and then decantation was performed eight times with 300 parts by weight of ion-exchanged water to remove Na ions and unadsorbed tungstate ions, and finally filtered and dried. .

As a result of comparative analysis of Test Sample 1 treated with tungstic acid and the untreated sample, it was confirmed that 0.43% by weight of tungstate anions were adsorbed in the sample treated with tungstic acid. This amount of adsorption corresponds to 0.48 tungstate anions adsorbed per 100 particles on the surface of the hexagonal ferrite particles. The adsorption amount of the above tungstate anion was determined by flame light analysis (
It was analyzed by ICP-AC3 method).

Therefore, the above-mentioned tungstic acid-treated hexagonal ferrite magnetic powder was used as an example, and the untreated hexagonal ferrite) T
Using FF powder as a comparative example, a system in which 1 part by weight of each of these was dispersed in 40 parts by weight each of acetone, methyl ethyl ketone, and cyclohexanone was examined for the conversion rate of each solvent to other compounds when kept at room temperature for 2 days. The results are shown in Table 1. Acetone and methyl ethyl ketone were analyzed by gas chromatography, and cyclohexanone 'ζ was analyzed by liquid chromatography.

Table 1 10 parts by weight of the above hexagonal ferrite was dispersed in 100 parts by weight of ion-exchanged water, and 0.3 parts by weight of sodium orthomolybdate (NazMoO, 2+1□0) was added, followed by ultrasonic dispersion. Adsorption of molybdate anion was carried out.

Thereafter, this dispersion system was allowed to stand, the supernatant was removed, and then decantation was performed eight times with 300 parts by weight of ion-exchanged water to remove Na ions and unadsorbed molybdate ions, and finally filtered and dried. .

Samples treated with molybdic acid and untreated sample f
As a result of comparative analysis with No. 4, it was confirmed that 0.12% of molybdate anions were adsorbed in the sample treated with molybdate. This amount of adsorption corresponds to 0.20 molybdate anions per 100 people 2 on the surface of the hexagonal ferrite particles. The amount of molybdate anion adsorbed above was determined by flame photometry (ICP-
Analyzed by AES method).

Therefore, the above-mentioned hexagonal ferrite magnetic powder treated with molybdic acid was used as an example, and untreated hexagonal ferrite l-i
Conversion rate of each solvent to other compounds when held at room temperature for 2 days for a system in which FF powder is used as a control example and one overlapping part of each of these is dispersed in 40 parts by weight each of acetone, methyl ethyl ketone, and cyclohexanone. I looked into it. The results are shown in Table 2. Note that acetone and methyl ethyl ketone were analyzed by gas chromatography, and cyclohexanone was analyzed by liquid chromatography.

(Leaving space below) Table 2 As is clear from Tables 1 and 2 above, the deterioration of the ketone solvent is prevented by adsorbing tungstate anions or molybdate anions on the surface of hexagonal ferrite.

Next, an example will be described in which a magnetic recording medium was created using hexagonal ferrite whose surface was treated with tungstate anions or molybdate anions.

Sodium Yutungstate (NaJO, -21!zo)
A treatment solution was obtained by dissolving 2.66 parts by weight in 5000 parts by weight of twice-distilled water. Barium ferrite (BaFe+o, *zCoo,
e4Tio, eao+q anti(n force 11c is 600
(Oe), saturation magnetization σ is 58.4 (emu/g)
, average particle size 0.05 μm, plate ratio 3. Specific surface area is 30.
0 m"/g) was added and thoroughly stirred and dispersed. The p++ of this dispersion was 9.1. llNO3 was added to this system to adjust the p++ to 7, and -04 Ion adsorption treatment was performed.

This system was further decanted 10 times with 5,000 parts by weight of ion-exchanged water to remove and purify the tl separation ions. Finally, it was suction-filtered and dried at +00°C for 24 hours to obtain an ion adsorption-treated barium ferrite magnetic powder sample of -04'-. When this magnetic powder sample was analyzed, the ion surface adsorption density of W04'- was 0.62, calculated by the metal type fftlA of tungsten, and the ion surface adsorption density was 0.68.
ion/nm".

A magnetic recording medium was prepared in the following manner using the magnetic powder sample prepared as described above.

Barium ferrite magnetic powder 100 parts by weight (w
o4''- ion adsorption treatment) Polyurethane resin (polyester linear polyurethane, number average molecular weight 60,000) 15 parts by weight cyclohexanone 360 parts by weight The above composition was thoroughly mixed to prepare a magnetic paint.

This was applied onto a polyester heath film with a pressure of 15 μm, and a magnetic field of 7 koe was applied vertically to the applied surface.
It was dried to obtain a sample recording medium.

Sodium tungstate (
2.66 parts by weight of Na2WO, 2H20) was added to ammonium paratanxstate ((NI+4)l.Hl.buttock, □
04. ) A magnetic powder sample was obtained in the same manner as in Example 3 except that 11.20 parts by weight was used. When this magnetic powder sample was analyzed, it was found to be 1.46% by weight in terms of tungsten metal weight, and the ion surface adsorption density of (LoLz046) was 0.13 ions/nm.

Using this magnetic powder sample, a sample magnetic recording medium was obtained in the same manner as in Example 3.

Sodium tungstate (used in Example 3)
NazW04.211zO) 2.66 parts by weight to 5.32
A magnetic powder sample was obtained in the same manner as in Example 3 except for changing the parts by weight. When this magnetic powder sample was analyzed, it was found to be 0.72% by weight in terms of tungsten metal weight, and the ion surface adsorption density of WO2''- was 0.79 ions/
It became n1112.

Using this magnetic powder sample, a sample magnetic recording medium was obtained in the same manner as in Example 3.

Sodium tungstate (
10.64 parts by weight of 2.66 parts by weight of NaJOa・211zO)
A magnetic powder sample was obtained in the same manner as in Example 3 except for changing the parts by weight. When this magnetic powder sample was analyzed, the ion surface adsorption density of WL"- was 1.02 ions/n in terms of the metal weight of tungsten, which was 0.93%.
m! It became.

Using this magnetic powder sample, a sample magnetic recording medium was obtained in the same manner as in Example 3.

Actual picture LLL Sodium molybdate (NatMoO4411J)
3.03 parts by weight was dissolved in 5000 parts by weight of twice-distilled water to obtain treatment i$1. This melt? & hexagonal ferrite and Tehalium '7 elite (BaFe+o, 3
zcOo, aaTio, 114019 coercive force Hc is 600 (Oe), saturation magnetization σ is 58.4 (emu
/g), average particle size 0.05 μm, plate ratio 3. Specific surface area is 30. 200 parts by weight (2/g) were added and thoroughly stirred and dispersed. The pl+ of this dispersion was 8.55.

Add IIN (h to this system, adjust ρ11 to 6.0,
An ion adsorption treatment of Mo0a''- was performed.

This system was further decanted 10 times with 5000 parts by weight of ion-exchanged water to remove and purify free ions. Finally, it was suction-filtered and dried at 100°C for 24 hours to obtain an ion adsorption-treated barium ferrite magnetic powder sample of MOO4z-. When this magnetic powder sample was analyzed, the molybdenum was 0.19% by weight in terms of metal weight, and the ion surface adsorption density of Mob, "- was 0.40 ions/
nm”.

A magnetic recording medium was prepared in the following manner using the magnetic powder sample prepared as described above.

barium ferrite magnetic powder (MOO4”-ion adsorption treated) polyurethane resin (Polyester linear polyurethane Rethane, number average molecular weight 60,000) cyclohexanone 100 parts by weight 15 parts by weight 360 parts by weight A magnetic paint was prepared by thoroughly mixing the above composition.

This was coated on a 15 μm thick polyester haze film, a 7 koe magnetic field was applied perpendicularly to the coated surface, and the sample was dried to obtain a sample magnetic recording medium.

Sodium molybdate (N
a2MoO4.2LO) 3.03 A magnetic powder sample was obtained in the same manner as in Example 7 except that the overlapping part was changed to 12.1 parts by weight. When this magnetic powder sample was analyzed, it was 0.28% by weight in terms of molybdenum metal weight, and M
Ion surface adsorption density of o0a'-0.59 ions/nt
It became n2.

Using this magnetic powder sample, a sample magnetic recording medium was obtained in the same manner as in Example 7.

Sodium molybdate (N
azMoOn411zO) 3.03 parts by weight was changed to 6.06 parts by weight, but LH was prepared in the same manner as in Example 7.
A magnetic powder sample was obtained. When this magnetic powder sample was analyzed, the molybdenum was found to be 0.18% by weight in terms of metal weight, and the ion surface adsorption density of MoO4''- was 0.38 ions/
nm”.

Using this magnetic powder sample, a sample magnetic recording medium was obtained in the same manner as in Example 7.

Sodium molybdate (N
a2MoO<411zO) 3.03 parts by weight was changed to 24.2 parts by weight, and the other methods were the same as in Example 7.6
A powder sample was obtained. When this magnetic powder sample was analyzed, it was 0.29% by weight in terms of molybdenum metal weight, and the ion surface adsorption density of Mo0at- was 0.61 ions/
nm”.

Using this magnetic powder sample, a sample magnetic recording medium was obtained in the same manner as in Example 7.

Fruit 41w Sodium molybdate (N
a2rIo04・2HzO) 3.03 parts by weight to 60.6
A magnetic powder sample was obtained in the same manner as in Example 7 except for changing the parts by weight. When this magnetic powder sample was analyzed, the molybdenum was 0.24% by weight in terms of metal weight, and the ion surface adsorption density of MoO,''- was 0.51 ions/
It became nIw2.

Using this magnetic powder sample, a sample magnetic recording medium was obtained in the same manner as in Example 7.

Sodium molybdate (N
aJo0441! go) 3.03 parts by weight of ammonium molybdate l:(Nun)iMotOzn・41(z
o) A magnetic powder sample was obtained in the same manner as in Example 7 except that 4.42 parts by weight was used. When this magnetic powder sample was analyzed, the molybdenum was found to be 0.7 in terms of metal weight.
The amount was 6% by weight.

A sample magnetic recording medium was obtained in the same manner as in Example 7 using this magnetic '#5) unsample.

The actual amount is sodium molybdate (NazOa, 211g).
0) Dissolve 60.6 parts by weight in 5000 parts by weight of twice-distilled water, and add 36 parts by weight of molybdenum trioxide (MOO3) to this solution.
．． 1 part by weight was added and sufficiently dissolved to obtain a treatment solution. Barium ferrite (
BaFe+o, 5zCoo, gnTio, eio
+ q + coercive force tic is 600 (Oe), saturated Cn
σ is 58.4 (emu/g), average particle size is 0.05μ
m, plate ratio 3. Specific surface area is 30.0m2/g) 200
Parts by weight were added and thoroughly stirred and dispersed. The pH of this dispersion was 5.5.

This system was further decanted 10 times with 5000 parts by weight of ion-exchanged water to remove and purify free ions. Finally, it was suction-filtered and dried at 100°C for 24 hours to obtain a barium ferrite magnetic powder sample treated with ion adsorption of Mob. 1.14% by weight in exchange JT
It became.

Using this magnetic powder sample, a sample magnetic recording medium was obtained in the same manner as in Example 7.

Expectoritis ■ Molybdenum trioxide (MoO) used in Example 13
z) Example 1 by changing 36.1 parts by weight to 72.2 parts by weight
It was treated in the same manner as in 3. pl+ of this dispersion system
was 4.6. A magnetic powder sample was then obtained in the same manner as in Example 13. Analysis of this (n-type powder sample) revealed that molybdenum was 1°17% by weight in terms of metal weight.
It became.

Using this magnetic powder sample, a sample magnetic recording medium was obtained in the same manner as in Example 7.

This 1 order 1 A magnetic powder sample was obtained by the same method as in Example 3 except that the barium ferrite magnetic powder used in Example 3 was not subjected to any treatment and this untreated barium ferrite magnetic powder was used. Ta.

Using this magnetic powder sample, a sample magnetic recording medium was obtained in the same manner as in Example 3.

The magnetic properties [saturation magnetic flux density Bm (15 kOe), perpendicular magnetization orientation degree Rs, perpendicular coercive force 11c] of the sample magnetic recording medium obtained as described above were measured. The results are shown in Table 3.

(Margin below) Table 3 It can be seen that the characteristics have improved.

As is clear from Table 3 above, hexagonal ferrite I-
Magnetic powder treated by adsorption with tungstate anions or molybdate anions is magnetic [Effect of the invention] As is clear from the above explanation, in the present invention, the surface of the hexagonal ferrite magnetic powder is treated with tungstate anions or molybdate anions. Since the surface is treated with anions, the surface properties, especially the activity as a basic heterogeneous catalyst, are suppressed, and it is possible to provide a hexagonal ferrite magnetic powder with less interaction with a solvent.

Further, since the hexagonal ferrite magnetic powder having the above-mentioned effects can be highly packed and highly oriented in the 41-layer, it is possible to achieve high output of the magnetic recording medium.

Therefore, by using the hexagonal ferrite magnetic powder of the present invention, a magnetic recording medium exhibiting excellent characteristics can be provided.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view showing an example of a magnetic recording medium to which the present invention is applied. FIG. 2 is a schematic cross-sectional view showing another example of a tn magnetic recording medium to which the present invention is applied. FIG. 3 is a schematic cross-sectional view showing still another example of a magnetic recording medium to which the present invention is applied. 1...Nonmagnetic support 2...Magnetic layer 3...Lubricant layer 4...Rust preventive layer

Claims (2)

[Claims] (1) A hexagonal ferrite magnetic powder characterized by being surface-treated with a tungstate anion and/or a molybdate anion. (2) A magnetic recording medium comprising a magnetic layer containing a magnetic powder and a binder resin on a non-magnetic support, in which the magnetic powder is a hexagonal crystal surface treated with a tungstate anion and/or a molybdate anion. A magnetic recording medium characterized by containing ferrite magnetic powder.