JPH03209626A - Ferromagnetic powder and magnetic recording medium formed by using this powder - Google Patents

Abstract

PURPOSE:To intensify the bonding strength between ferromagnetic powder and a binder and to improve the durability of the magnetic recording medium for which these powder and binder are used by forming an indium compd. layer on the surface of the ferromagnetic powder essentially consisting of iron. CONSTITUTION:The ferromagnetic powder consists essentially of the iron and may contain small amts. of other components, such as silicon compd., aluminum compd., cobalt, and nickel. The formation of the film of the indium compd. on the ferromagnetic powder is executed by dispersing alpha-FeOOH, gamma -FeOOH, alpha-Fe2O3, etc., which are raw materials, into water and adding an indium (III) salt soln. thereto, then adding ammonia water thereto, thereby forming the coating of the indium compd. on the surface of the raw material powder. The bonding strength to the binder, more particularly the binder having a functional group exhibiting acidity in the molecular structure is intensified in this way.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a ferromagnetic powder for a recording medium.

More specifically, the present invention relates to the development of ferromagnetic powders that strengthen the binding force with binders.

[Conventional technology]

Various means have been devised to improve the durability of a magnetic recording medium in which a magnetic layer is formed by applying ferromagnetic powder to a non-magnetic support together with a binder for dispersing and binding the ferromagnetic powder. One of these methods is to introduce acidic functional groups such as phosphoric acid groups and carboxylic acid groups into the molecules of organic polymer resin as a binder to strengthen the binding force with the ferromagnetic powder. There is.

However, with the recent expansion of uses for magnetic recording media,
It has become difficult for conventional methods to adequately cope with the harsh conditions of use.

[Problem that the invention seeks to solve]

This invention solves the drawback of the lack of binding strength between the ferromagnetic powder and the binder that the conventional products had.

Therefore, it is an object of the present invention to provide a magnetic recording medium with excellent durability and a ferromagnetic powder used therein.

[Means to solve the problem]

As a result of intensive studies to achieve the above object, the present inventors discovered that 1. By coating the outermost surface of a ferromagnetic powder with an indinicum compound, the binder, especially a bond having an acidic functional group t- This invention was made based on the knowledge that the binding force with the agent is strengthened and the durability of &i magnetic recording media is improved.

That is, the first aspect of the present invention relates to a strong 1iIi powder having an indium compound wit on its outermost surface.

In addition, the second aspect of the present invention is a ferromagnetic powder according to the first invention described above on a non-magnetic support! The present invention relates to a magnetic recording medium provided with a magnetic layer comprising a binder, preferably a binder having a functional group.

In the ferromagnetic powder of the present invention, the ferromagnetic powder on which the indium compound is to be formed is as follows:
Acicular ferromagnetic powder with an average particle diameter of 0.1 to 1.0μ and an average axial ratio (average major axis diameter/average minor axis diameter of about 95 to 15) is preferable.This ferromagnetic powder has iron as its main component. , may contain small amounts of other components such as silicon compounds, aluminum compounds, cobalt and nickel.The coercive force r
i200 ~ 2.000z le x ted, saturation magnetization u40 ~
It is 200 emu/I.

The formation of the film of the indium compound of this ferromagnetic powder is carried out using the raw materials a-FeOOH, 7-Fe00H9a-FIz.
After dispersing Oi etc. in water and adding indium side salt bath liquid to this, ammonia water is added to form a film of indium compound on the surface of the raw material powder, and this powder is heated and reduced. The amount of indium compound made by making it ferromagnetic is 0.05 to 10 w based on the weight of iron component in 1 ferromagnetic powder.
t%, particularly preferably 0.1 to 5 wt%. If this amount is less than 1.05 wt%, the binding force with the binder will not be strong, and if it is more than -10 wt%, magnetic properties such as saturation magnetization will deteriorate, which is not preferable.

The magnetic recording medium according to the second invention is one in which a magnetic layer containing the above-mentioned ferromagnetic powder having an indium compound coating and a binder having a functional group is provided on a non-magnetic support such as a polyester film. Yes, it can be manufactured according to conventional methods.

For example, the above ferromagnetic powder, a binder, and 6 additives are mixed as necessary in a total medium.
Prepare a 1-note paint, apply this paint onto a non-magnetic support,
After drying to form a magnetic layer of a desired thickness, appropriate post-processing such as calendering is performed to form the desired shape of the magnetic recording medium and f'L is good.

Examples of the above-mentioned binders include vinyl chloride-vinyl acetate copolymers, polyvinyl butyral resins, cellulose resins, polyurethane resins, polyester resins, polyisocyanate compounds as crosslinking agents, radiation-curable resins, etc.
Any of the binders conventionally known as binders for magnetic layers of magnetic recording media can be used alone or in combination of two or more.

However, some or all of these binders contain phosphate groups,
It is necessary to have a functional group such as a carboxylic acid group or a sulfonic acid group in the molecule.

Examples of organic solvents include ketone solvents such as cyclohexanone, methyl ethyl ketone, and methyl imbutyl ketone, ester bath agents such as ethyl acetate and butyl acetate, aromatic hydrocarbon bath agents such as benzene, toluene, and xylene, and inpropyl alcohol. Suitable for dissolving the binder used in the cylinder, such as alcohol bath agents, acid amide solvents such as methylformamide, sulfoxide bath agents such as dimethyl sulfoxide, and ether solvents such as tetrahydrofuran dioxane. It can be used alone or as a mixture of two or more types.

Additionally, additives may be added as needed.

Examples include dispersants, S lubricants, abrasives, antistatic agents, and fillers.

〔Example〕

Example 1 100 g of hydrated iron oxide coated with a silicon compound having an average major axis diameter of 0.4μ and an average axial ratio of 15.
of water and dispersed using a homomixer. 5 g of indium nitrate was added to this dispersion, stirred and dissolved in a homomixer, and then heated to 60°C. Add 6g of ammonia water (concentration 28%) on top of it.

After stirring for 2 hours, the mixture was filtered and dried. After that, it was treated in air at 500℃ for 10 hours at 11%, and then in a hydrogen stream for 4 hours.
a11 which has been subjected to 4Q dark reduction at 50°C and has an indium compound coating on its outermost surface! ): α-Fe powder was obtained.

Using this ferromagnetic powder, a magnetic recording medium was produced according to the "F Bulletin" method.

Strong S injection powder 100@Kurabe Vinyl chloride-vinyl acetate-vinyl alcohol copolymer with functional group 10 parts by weight Polyurethane resin
6fJEt myristic acid
5 layers 1 part carbon black
1 part by weight α-A11oz (particle size 0.4μ)
5 parts of toluene 85 parts of methyl isobutyl ketone 85 parts of Dobe and Kigumi were dispersed in a ball mill for 72 hours.

To this dispersion, 401 parts of toluene and 2 Mt parts of a polyincyanate compound were further added and redispersed to obtain a magnetic paint. This magnetic paint was applied onto a polyester base film having a thickness of 12 .mu.m so that the dry thickness would be 4 .mu.m, and after drying and surface processing, the film was cut into 1/2 inch width to prepare a magnetic tape.

Example 2 In producing the ferromagnetic powder of Example 1, n2 hematite coated with a silicon compound was used as the raw material iron oxide, and in addition to the
Magnetic α-F powder was obtained in the same manner as in Example 1.

Example 3 Magnetic α-Fe powder was obtained in the same manner as in Example 1, except that t-hydrated iron oxide coated with an aluminum compound was used as the raw material iron oxide.

The magnetic tape is made of magnetic α-
The magnetic recording medium was produced in the same manner as in Example 1 except that Fe powder was used.

Comparative Example 1 Hydrous iron oxide coated with a silicon compound having an average major axis diameter of 0.4μ and an average axis ratio of 15 was heat treated in air at 500°C for 10 hours, and this powder was heated at 450°C in a hydrogen stream for 4 hours. 7 tl of magnetic α-Fe powder was obtained by reduction.

The magnetic tape is tMifB! i: A magnetic recording medium prepared in the same manner as the magnetic recording medium of Example 1, except that the S Note α-F@ powder obtained in this comparative example was used as the powder.

Comparative Example 2 Comparison? A magnetic α-F powder was obtained in the same manner as in Comparative Example 2, except that hydrated iron oxide coated with an aluminum compound was used as the raw material iron oxide in the method for producing the magnetic α-F powder.

A magnetic tape was produced in the same manner as the magnetic recording medium of Example 1 except for t, using the magnetic α-F powder obtained in this comparative example as a 1 strength A8 powder.

Table 1 shows the results of analysis using a fluorescent X-ray device of the adsorption amount of binder having a functional group and the indium content in the ferromagnetic powder of the magnetic α-Fe powder obtained in each of the Examples and Comparative Examples mentioned above. .

The still life of the magnetic tapes obtained in Example 1.3 and Comparative Example 1.2 was measured using a Sendust magnetic head having a head gap of 0.3 μm and a head width of 20 μm. Measurements were carried out at -5°C, and the time required for the reproduction output to decrease by 3 dB from the initial output was expressed. The results are shown in Table 2.

Table 2 [Effects of the invention] As explained above, the surface of the G1 magnetic powder, which is mainly made of iron, is covered with an indium compound. It is clear that the durability of the magnetic recording medium using the saproper powder is much better.

Claims (3)

[Claims] (1) A ferromagnetic powder characterized by forming an indium compound layer on the surface of a ferromagnetic powder mainly made of iron. (2) The ferromagnetic powder according to claim (1), wherein the amount of the indium compound deposited is 0.05 to 10 wt% expressed as indium/iron. (3) In a magnetic recording medium formed by applying a magnetic layer mainly composed of ferromagnetic powder and a binder to a non-magnetic support, the indium compound layer according to claims (1) and (2) is applied as a ferromagnetic powder. A magnetic recording medium characterized by using ferromagnetic powder.