JPH03104201A - Magnetic powder for high density magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve S/N of a magnetic recording medium itself by specifying the bulk density of hexagonal crystal ferrite magnetic powder containing specific composition. CONSTITUTION:Hexagonal crystal ferrite magnetic powder represented by AO.n(Fe1-xMx)2O3 (where A is at least one type of element selected from Ba, Sr, Ca and Pb, M is at least one type of element selected from CO, Ti, In, Ni, Cu, Zn, Nb, Zr, V, Ta, Cr, Sb, Hf, MO, W, Ir, Sn and Mg, and n is a number of 5.0-6.5, and x is a number of 0.02-0.24) has 0.8-1.5g/cm<3> of bulk density. Thus, since the bulk density is set relatively high, it is easy to enhance the filling density of magnetic powder in a high density recording medium to be formed. Accordingly, as the filling density of the powder is improved, S/N (output) of the medium is improved.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to magnetic powder used in the production of high-density magnetic recording media, and particularly to high-density magnetic recording media with a high S/N ratio. The present invention relates to magnetic powder for high-density magnetic recording media suitable for manufacturing.

(Prior Art) Conventionally, as a method for manufacturing high-density magnetic recording media or perpendicular magnetic recording media, a magnetic paint is prepared by mixing fine powder of hexagonal ferrite with a binder, a solvent, and various additives. A method of applying this magnetic paint onto a support such as a film is known. By the way, in the above-mentioned hexagonal ferrite magnetic powder, the coercive force is reduced to a value suitable for magnetic recording by replacing some of the constituent atoms of the hexagonal ferrite with specific other atoms.

The method for manufacturing hexagonal ferrite magnetic powder used for such magnetic recording involves mixing the basic components of hexagonal ferrite, some substitution for reducing coercive force, some additive components for improving the characteristics of ferrite, and glass forming components. (raw material mixture), heated and melted, this melt is rapidly cooled to form a non-quality material, this is heat treated to precipitate hexagonal ferrite fine particles, and then this is pulverized to obtain the obtained fine particles. A so-called glass crystallization method is often employed in which hexagonal ferrite magnetic powder is separated and extracted by treating the powder with a dilute acid such as phosphoric acid or acetic acid to dissolve and remove glass-forming components.

(Problems to be Solved by the Invention) By the way, for example, hexagonal ferrite magnetic powder such as Ba ferrite obtained by the above-mentioned glass crystallization method has an average particle diameter of 50
It is desired that the thickness is about 0 to 800λ, and the plate ratio is about 5 to 1O to obtain high orientation and saturation magnetization. On the other hand, in order to sufficiently and reliably retain and exhibit the function of high-density magnetic recording, it is desirable that the hexagonal ferrite magnetic powder be uniformly dispersed in the magnetic recording medium layer. Countermeasures are also being taken. Furthermore, in high-density magnetic recording media, attention is being focused on improving the quality and performance of magnetic recording, and in particular, improving the S/N ratio is becoming more important. However, in the case of high-density magnetic recording media constructed using conventionally known hexagonal ferrite magnetic powders such as the above-mentioned Ba ferrite, it may not be possible to sufficiently improve the S/N ratio. This is often the case, and there are problems such as poor reproducibility.

As a result of conducting studies in response to these circumstances, the present inventor discovered that the bulk density of the hexagonal ferrite magnetic powder obtained by the glass crystallization method has a large effect on the S/N ratio. Ta. Based on this knowledge, the present invention aims to provide a magnetic powder suitable for manufacturing (configuring) a high-density magnetic recording medium with a high S/N ratio.

[Structure of the Invention] (Means for Solving the Problems) The present invention has the following general formula: AOIIn(Fe1-xMx)203 (where A is selected from Ba.Sr.Ca, Pb)2O3( However, A is Co, Ti, In.Ni
．． Cu. Zn. Nb. Zr, V. Ta. Cr. Sb.
Hf'. Mo, l. Ir. At least one element selected from sn, Mg, n is a number from 5.0 to 6.5, and X is a number from 0.02 to 0.24). Therefore, the bulk density of the hexagonal ferrite magnetic powder is 0.8 to 1.5.
g/cm".

(Function) The magnetic powder for high-density recording according to the present invention has a density of 0.8 to 1.5 g/as. In other words, the bulk density of the magnetic powder is selected to be relatively high. , it is easy to increase the packing density of magnetic powder in high-density recording media.However, the S/N ratio of a magnetic recording medium exists per unit area of the recording medium. , is proportional to the square root of the number of magnetic particles dispersed (contained), so
With the improvement in the packing density of the magnetic powder mentioned above, the S/
N (output) will be improved.

(Example) Examples of the present invention will be described below.

First, the ferrite component Fe203 of Ba ferrite,
Substituent components TIO 2 , Coo for reducing coercive force and glass forming component BaO . B 2 0 3 is shown in Table 1
Predetermined amounts of Bengara, titanium oxide, cobalt oxide, barium carbonate, and boric acid were weighed out so that the composition ratio (weight %) was as follows.

Table 1 (All weight ratio vt%) After thoroughly mixing the weighed components, they were placed in a platinum crucible and melted by heating at 1350°C using a high-frequency heater. , rotation speed 5
The mixture was poured onto water-cooled twin rolls at 00 rpm and rapidly cooled to produce a non-quality material.

The non-quality material obtained above was heated at 780°C for 4 hours to obtain Ba.
After precipitating ferrite crystals, the crystallized product is crushed, and the crystallized powder is mixed with about 4 times the amount of dilute acetic acid solution (10%).
The glass components were melted using ultrasonic waves for 5 hours.
A removal process was performed. After dissolving and removing this glass content, repeated washing with hot water of 80°C or higher to remove glass-formed components, etc., followed by dehydration and drying to reduce the particle size to 0.01 to 8 μm and the retention strength. He about 800 oersted (
Oe). A hexagonal Ba ferrite magnetic powder with a saturation magnetization of 58 emu/g was obtained.

The hexagonal Ba ferrite magnetic powder obtained above was divided into approximately 6 equal parts, each with a pressure (kg/cd) of 0 to 3000.
A press treatment was applied. Regarding the magnetic powder obtained by performing the above press treatment, the bulk density (g/cj) and coercive force lie
While (Oe) was measured, tape-shaped magnetic recording media were prepared using conventional methods using the magnetic powder, and the S/N ratio (dI3) was measured. Table 2 shows the results.

Table 2 As can be seen from Table 2 above, as the press pressure in magnetic powder increases during press pressure treatment, the scraping density also increases, and the S/N of the magnetic recording medium to which the magnetic powder is applied also increases. However, the bulk density is 1. When it exceeds 5 g/cj, aggregation becomes strong and a decrease in S/H is observed. Furthermore, if the scraping density is less than 0.8 g/cj, it is difficult to increase the filling rate of magnetic powder in the magnetic recording medium.
, the S/N ratio decreases. Therefore, the bulk density of the magnetic powder is always selected within the range of 0.8 gld to 1.5 g/cj.

In the above, as a means to increase the bulk density of the magnetic powder, the dried magnetic powder was subjected to press pressure treatment, but the slurry obtained by the glass crystallization method before the drying treatment is A press treatment method may also be used.

Note that the present invention is not limited to the above embodiments,
Similar effects occur for all hexagonal ferrite magnetic powders for high-density recording obtained by the so-called glass crystallization method.
The effect is recognized.

[Effects of the Invention] As is clear from the above description, the hexagonal ferrite magnetic powder according to the present invention not only has the required saturation magnetization characteristics and coercive force, but also has a relatively high scraping density, and is suitable for use in magnetic recording media. Since the filling rate per unit area can be easily increased, the S/N of the magnetic recording medium itself can be improved. Improvements are possible. Thus, the magnetic powder according to the present invention can be said to be a magnetic powder suitable for manufacturing high-density magnetic recording media or perpendicular magnetization recording media.

Claims (1)

[Claims] General formula: AO・n(Fe_1_−_xM_x)_2O_3 (where A is at least one element selected from Ba, Sr, Ca, Pb, M is Co, Ti, In, Ni,Cu
, Zn, Nb, Zr, V, Ta, Cr, Sb, Hf, M
At least one element selected from o, W, Ir, Sn, Mg, n is a number from 5.0 to 6.5, and x is from 0.02 to
0.24), the hexagonal ferrite magnetic powder has a bulk density of 0.8 to 1.5.
A magnetic powder for use in high-density magnetic recording media, characterized in that it has a magnetic density of g/cm^3.