JPS6245006A - Ferromagnetic powder - Google Patents

Abstract

PURPOSE:To contrive improvement in electric resistance of the titled magnetic powder by a method wherein a V2O5-MmOn gel-form oxide is coated or coexisted on the surface of ferromagnetic powder. CONSTITUTION:V2O5-MmOn (M indicates at least a kind of Li, Ti, Mg, Cr, Ba, Zn, Ge, Si and B, and m and n indicate an integral number) oxide is coated or coexisted on the surface of ferromagnetic powder. Said V2O5-MmOn oxide is a gel-form oxide, and it is also formed of amorphous V2O5-MmOn oxide by a very rapid cooling technique using a liquid, copper plate, or the like. As a result, the electric resistance of said material becomes very small, it is hardly electrified, and the variation with time of the magnetic characteristics such as coercive force and the like can be prevented. Accordingly, the noise of discharge, the adhesion of a tape and the like can be prevented, and the excellent magnetic characteristics can be obtained, thereby enabling a high density recording.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a ferromagnetic powder used in coated magnetic recording media such as magnetic tapes and magnetic disks.

[Conventional technology]

Conventionally, γ-Feg, 02 particles have been widely used as ferromagnetic powders used in coated magnetic recording media. These γ-Fears particles have advantages such as excellent chemical and magnetic stability and low cost.

In general, in magnetic recording media, the coercive force Hc of ferromagnetic powder is an important factor that affects the recording and reproducing characteristics.By increasing this coercive force Hc, demagnetization can be suppressed and recording density can be improved. It is known that it is possible to In order to improve the performance of magnetic recording media such as video tapes and audio tapes, it is necessary to further increase the coercive force He of the ferromagnetic powder.

Therefore, the so-called cobalt-coated type r-Fe, in which cobalt is coated on the surface of the above-mentioned r-Fe, O, particles! o1 particles are also considered. This cobalt coated type r Fee'
In s particles, it has become possible to increase the coercive force Hc by concentrating the effect of cobalt ions on the particle surface.

However, when a magnetic tape is manufactured using these γ-Fe, O, particles or cobalt-coated 1-Fe203 particles as magnetic powder, the electrical resistance of this magnetic layer becomes extremely large. When recording and reproducing are performed using a magnetic tape having a high resistance, the magnetic layer is easily charged, which has disadvantages such as discharge noise and tape sticking.

Conventionally, such charging has often been prevented by improving the mechanical parts of the recording/reproducing device. However, it is clear that this method does not essentially solve the above problems, and it is desired to reduce the charging of the magnetic layer by lowering the electrical resistance of the magnetic powder itself.

Therefore, it has been considered that ferrous ions (Fe'') are deposited on the surface of the above-mentioned cobalt-coated type 7 Fails particles to lower the electrical resistance of the magnetic powder itself and reduce the charging. In this case, a problem arises in that the coercive force Hc and electrical resistance of the magnetic powder change significantly over time.

[Problem that the invention seeks to solve]

As described above, conventional magnetic powders have a problem of being easily charged due to their high electrical resistance, and that attempts to improve electrical resistance cause changes in magnetic properties over time.

Therefore, the present invention was proposed to solve the above problems, and provides a ferromagnetic powder that improves electrical resistance without impairing magnetic properties, is difficult to be charged, and has excellent magnetic properties. The purpose is to

[Means for solving problems]

In order to achieve the above object, the inventors of the present invention have conducted extensive research and have discovered that Vies, which was produced by a liquid ultra-quenching method, etc.
M, O, and oxides very easily form colloids using water as a solvent, and this hydrated colloid intercalates M metal ions and remains stable for a long time, and has a high electrical conductivity ( 10-'-10-"Ω-1,c
By depositing and forming this V2O5M,O,-based oxide on the surface of ferromagnetic powder, the electrical resistance of this ferromagnetic powder can be improved without impairing the magnetic properties such as coercive force Hc. We have come to the conclusion that it is possible to do so.

The ferromagnetic powder of the present invention was created based on this knowledge, and has a structure of 205-M, 0L on the surface of the ferromagnetic powder.
1 (However, M is Li, Ti, Mg, Cr.

At least one of Ba, Zn, Ge, Si, and B is represented, and m and n each represent an integer. ) type oxide is deposited or mixed therein.

Here, the above-mentioned V z MmO3 -M -0, system oxide is a gel-like oxide, and its manufacturing method is an amorphous 20 produced by liquid ultra-quenching technology, copper plate ultra-quenching technology, etc.
Made from ゜-M, OR-based oxides.

Further, as a method for depositing the VzMmO3 M-0-based oxide, any conventional method may be used. For example, r Fezes particles are dispersed in an alkaline solution, and then the V,0 ．． -V z MmO3-M, O, iron oxide is coated by adding an aqueous solution in which M, O, iron oxide is dissolved, heating and stirring at a temperature below the boiling point, and holding for a predetermined time. Examples of the alkali used at this time include sodium hydroxide, potassium hydroxide, and lithium hydroxide.

Further, by mixing and dispersing a solution in which an amorphous oxide is separately dispersed in water and gelled into a solution in which the magnetic powder is dispersed in advance, a magnetic powder in which the above-mentioned oxides are mixed can be produced.

[Effect]

Therefore, since the ferromagnetic powder of the present invention has a VzMmO3M, OR gel-like oxide having high electrical conductivity adhered to or mixed on the surface of the ferromagnetic powder, the ferromagnetic powder does not impair its magnetic properties. This makes the electrical resistance extremely low, making it difficult to charge.

〔Example〕

Next, the present invention will be explained using specific examples, but the present invention is not limited to these examples.

Example First, v20. and L 1zcMmO3 are melted at about 1000°C in a platinum crucible,
COI was separated from. Next, the above melt is made amorphous by a copper plate ultra-quenching method to form V, O, -M, and O.

System amorphous oxide (VzMmO3)o,,s(L i g
o) After producing a and ts, this oxide was further finely ground, and then dispersed in water to form a gel-like hydrate.

On the other hand, γ-Fat's particles were mixed with sodium hydroxide at 115%.
Cobalt-coated γ-F6
An alkaline slurry containing i0s particles was prepared.

Next, in the alkaline slurry, the above-mentioned gel-like hydrate (VzMmO3)o,ts(L i to)
o, zs was administered to the surface of cobalt-coated r-Fe2Ox particles (V, O5). ,ys(L 1zo). , 2.
After being deposited or mixed together, the powder was dehydrated and dried to produce ferromagnetic powder.

The ferromagnetic powder obtained above is melted in a solvent together with a vinyl chloride/vinyl acetate copolymer resin (VAGH manufactured by Union Carbide Co., Ltd.) and Blysurf (trade name) to prepare a magnetic paint. It was applied onto a polyethylene terephthalate sheet to form a magnetic layer.

The electrical resistance of the magnetic layer thus obtained is 5.0X
It was as small as 10 Ω/sq, and no change in magnetic properties over time was observed.

Comparative Example Cobalt-coated r-Fe produced in the previous example! o1 particles were treated with vinyl chloride/vinyl acetate copolymer resin (VAGH manufactured by Union Carbide) in the same manner as in the previous example.
and Plysurf (trade name), dissolved in a solvent,
A coating liquid was prepared, and this coating liquid was applied onto a polyethylene terephthalate sheet to form a magnetic layer.

The electrical resistance of the magnetic layer thus obtained is 1.0X
It was 10''Ω/sq. Changes in magnetic properties over time were also observed.

〔Effect of the invention〕

As is clear from the above examples, in the present invention, VzMmO having high electrical conductivity is used on the surface of the ferromagnetic powder.
3 Since it is coated with or mixed with M-0-based gel oxide, the electrical resistance of this ferromagnetic powder is extremely small compared to conventional ferromagnetic powder, making it difficult to charge and reducing coercive force. There are no changes in magnetic properties over time, such as
There is no loss of magnetic properties.

Therefore, when this ferromagnetic powder is used in magnetic recording media, discharge noise and tape sticking are less likely to occur.
Moreover, it has excellent magnetic properties and can exhibit sufficient properties as a magnetic recording medium capable of high-density recording.

The ferromagnetic powders also have the advantage of being easily manufactured using conventional cobalt deposition techniques.

September 20, 1985 Michibu Uga, Commissioner of the Patent Office1, Indication of the case 1985 Patent Application No. 1846432, Title of invention Ferromagnetic Powder3, Person making the amendment Case and Relationship Patent applicant address: 6-7-35, Kitashinyo, Tokyo Parts Store Name: (
218) Norio Ohga, representative of Sony Corporation 6. Amend the description in the "Claims" column of the specification to be amended and the "Claims column of the Specification of Invention" as shown in the attached sheet. .

In the second line of page 6 of the specification, the statement "with magnetic powder" is amended to read "with magnetic powder."

(Above) Attachment Claims r V2O4, M-0° series amorphous oxide formed by rapid cooling on the surface of ferromagnetic powder as a starting material V t MmO3
-M, Oo (M is Li, Ti, Mg, Cr, 13
a.

Represents at least one of Zn, Ge, St, and B, m
and n each represent an integer. ) Ferromagnetic powder characterized by being coated with or mixed with a gel-like oxide. ”

Claims (1)

[Claims] V_2O_5-M_m by rapid cooling method on the surface of ferromagnetic powder
V_2O using O_3-based amorphous oxide as a starting material
_5-M_mO_n (M is Li, Ti, Mg, Cr
, Ba, Zn, Ge, Si, and B, and m and n each represent an integer. ) Ferromagnetic powder characterized by being coated with or mixed with a gel-like oxide.