JPS61217929A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a magnetic recording medium having good vertical orientability with good productivity by making combination use of hexagonal ferrite magnetic powder and acicular ferromagnetic powder. CONSTITUTION:The hexagonal ferrite magnetic powder having >=5 plate ratio and <=600 oersted coercive force is selected. The ferromagnetic powder having >=4 acicular ratio, 100emu/g saturation magnetization and <=700 oersted coercive force is selected. The ratio of the hexagonal ferrite magnetic powder and the ferromagnetic powder is made <=30pts.wt. the latter with respect to 70-100pts. wt. the former, then the magnetic recording medium of which the magnetic characteristics are less deteriorated with time (for example, the reproduced output is less decreased with time) and which has a good erasing characteristic, good high-frequency characteristic, high density and high output is obtd. The ratio of the ferromagnetic powder is more preferably about 30-5wt% with respect to about 70-95wt% the hexagonal ferrite magnetic powder.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magnetic recording medium such as a magnetic tape, a floppy disk, or a hard disk for use in audio, video, or computers.

[Prior art and its problems]

Conventionally, as a magnetic recording medium, a magnetic paint containing acicular γ-Fetus magnetic powder is applied onto a non-magnetic substrate, and the magnetization is oriented in the in-plane longitudinal direction by an orientation treatment such as mechanical orientation or magnetic field orientation. The main type is the so-called horizontal magnetic recording method.

However, this type of horizontal magnetic recording type magnetic recording medium is
If the recording signal has a short wavelength, the self-demagnetizing effect increases and the reproduction output decreases, so it is not suitable for high-density recording.

Therefore, as a solution to these drawbacks, a so-called perpendicular magnetic recording type magnetic recording medium has been proposed.
For example, ferromagnetic powder and hexagonal ferrite magnetic powder, especially hexagonal ferrite powder with an average particle size of 0.2 μm or less 5 to 1
A magnetic recording medium is proposed in which 100 parts by weight of a ferromagnetic powder having a saturation magnetization of 70 emu/g or more and an average particle size larger than the average particle size of the hexagonal ferrite powder are dispersed in a resin binder. (Unexamined Japanese Patent Publication No. 58-203625
No.) has been done.

In other words, the technical idea of this proposal is that simply using ferromagnetic powder and hexagonal ferrite magnetic powder will lead to a decrease in magnetic properties due to poor dispersibility of the magnetic paint. It is stated that if the structure is configured as follows, the dispersibility of the magnetic coating material will be improved, and a magnetic recording medium with good magnetic properties can therefore be obtained.

However, according to research conducted by the present inventors, it has been found that even this proposed magnetic recording medium is not fully satisfactory for high-density recording.

[Disclosure of the invention]

The present inventor has discovered that a combination of hexagonal ferrite magnetic powder and ferromagnetic powder, such as barium ferrite magnetic powder, strontium ferrite magnetic powder, calcium ferrite magnetic powder, lead ferrite magnetic powder, or substituted barium ferrite magnetic powder, is mixed. While conducting research and development of magnetic recording media, we selected hexagonal ferrite magnetic powder with a plate ratio of 5 or more and a coercive force of 600 oersted or less, and also selected ferromagnetic powder as ferromagnetic powder. has an acicular ratio of 4 or more and a saturation magnetization of 10100e/
g or more and has a coercive force of 700 oersted or less, and the ratio of the hexagonal ferrite magnetic powder having the above characteristics to the ferromagnetic powder having the above characteristics is 70 to 100 parts by weight for the former and 70 to 100 parts by weight for the latter. If the amount is 30 parts by weight or less, there will be little change in magnetic properties over time (for example, less decline in FM output due to changes over time), good erasing properties, and good high frequency properties, with high density and high output. It was discovered that a magnetic recording medium of

In other words, by using hexagonal ferrite magnetic powder and acicular ferromagnetic powder together, the perpendicular magnetization component of hexagonal ferrite magnetic powder can be effectively used, increasing the reproduction output in the high frequency range and increasing the density. Although the horizontal magnetization component of the acicular ferromagnetic powder can be used effectively and the reproduction output in the low frequency range is improved, the relative amount of ferromagnetic powder to the hexagonal ferrite magnetic powder is If the number of ferrite particles increases too much, the deterioration of the magnetic properties will be severe, for example, the FM output will drop significantly due to changes over time, and the reproduction output in the high frequency range will also be greatly reduced. 70-100% by weight of ferromagnetic powder, more preferably about 70-95% of hexagonal ferrite magnetic powder and about 30-5% by weight of ferromagnetic powder. It is desirable that it be a percentage.

Furthermore, it is desirable that the ratio of hexagonal ferrite magnetic powder and ferromagnetic powder be as described above, not only from the viewpoint of the magnetic properties but also from the viewpoint of C/N frequency characteristics. In order to improve the C/N characteristic in this high frequency region, it is important to not only adjust the ratio of the hexagonal ferrite magnetic powder to the ferromagnetic powder, but also to adjust the coercive force of the hexagonal ferrite magnetic powder to 600 oersted or less, more preferably about 400 to 600 oersted, and the saturation magnetization of the ferromagnetic powder is 1
It is desirable that the coercive force is 0.100 e/g or more and 700 Oe/g or less, more preferably about 500 to 700 Oe/g.

Furthermore, the fact that the coercive forces of the hexagonal ferrite magnetic powder and the ferromagnetic powder are as described above means that C/
This is desirable not only from the viewpoint of improving N characteristics, but also from the viewpoint of input/output characteristics and erasing characteristics.

Further, by using a hexagonal ferrite magnetic powder whose platelet ratio is 5 or more, preferably about 7 to 15, and a ferromagnetic powder whose acicular ratio is 4 or more, preferably about 6 to 15, mechanical orientation can be achieved. Easy processing and improved frequency characteristics.

Further, it is desirable that both the hexagonal ferrite magnetic powder and the ferromagnetic powder used above have an average particle size of about 0.3 μm or less.

[Example 1] Barium ferrite magnetic powder whose C axis is the axis of easy magnetization (plate ratio 10, coercive force 580 oersted, saturation magnetization 57 emu)
/g1 average particle size 0.1 μm) 85 parts by weight, metallic iron magnetic powder (acicular ratio 8, coercive force 670 oersted, saturation magnetization 12
5 emu/g1 average particle size 0.2 μm) 15 parts by weight, 25 parts by weight of binder, 1 part by weight of dispersant, 4 parts by weight of abrasive, 5 parts by weight of carbon black, 1 part by weight of lubricant, 30 parts by weight of solvent.
0 parts by weight of the mixture is sufficiently cross-dispersed to make a magnetic paint, a curing agent is added to this magnetic paint, it is applied onto a non-magnetic substrate such as polyethylene terephthalate, and after drying, it is calendered and slit into 7-inch pieces. to obtain magnetic tape.

[Example 2] A magnetic tape was obtained in the same manner as in Example 1 except that 95 parts by weight of the barium ferrite magnetic powder and 5 parts by weight of the metal iron magnetic powder were used.

[Example 3] In Example 1, instead of making a magnetic tape by slitting it to a width of i inch, a floppy disk is obtained by punching it to a diameter of 5.25 inches.

[Comparative Example 1] A magnetic tape is obtained by carrying out the same procedure as in Example 1 using metal iron magnetic powder having an acicular ratio of 3, a coercive force of 610 oersted, a saturation magnetization of 125 emu/g, and an average particle size of 02 μm.

[Comparative Example 2] A magnetic tape is obtained by carrying out the same procedure as in Example 1 using barium ferrite magnetic powder having a plate ratio of 4, a coercive force of 580 oersted, a saturation magnetization of 57 emu/g, and an average particle size of 0.1 μm.

[Comparative Example 3] A magnetic tape is obtained by carrying out the same procedure as in Example 1 except for using 100 parts by weight of metal iron magnetic powder instead of using barium ferrite magnetic powder.

[Comparative Example 4] The same procedure as in Example 1 was carried out except that 50 parts by weight of the barium ferrite magnetic powder and 50 parts by weight of the metal iron magnetic powder were used to obtain a magnetic tape.

[Comparative Example 5] The same procedure as in Example 1 was carried out except that the barium ferrite magnetic powder was 60 parts by weight and the metal iron magnetic powder was 40 parts by weight.
Get magnetic tape.

[Comparative Example 6] Example 1 The same procedure was carried out using metallic iron magnetic powder having an acicular ratio of 8, a coercive force of 1500 oersted, a saturation magnetization of 125 emu/g, and an average particle size of 0.2 μm at k”C.
Get magnetic tape.

[Comparative Example 7] In Example 1, the plate ratio was 10. A magnetic tape is obtained in the same manner using barium ferrite magnetic powder having a coercive force of 900 oersted, a saturation magnetization of 57 e 171 u/gs, and an average particle size of 0.1 μm.

[Comparative Examples 8 to 10] In Example 3, the amounts of barium ferrite magnetic powder and metal iron magnetic powder were 0 parts by weight and 100 parts by weight (Comparative Example 8),
50 parts by weight and 50 parts by weight (Comparative Example 9), 65 parts by weight and 3
The same procedure was carried out using 5 parts by weight (Comparative Example 10) to obtain a floppy disk.

[Comparative Example 11] A floppy disk was obtained by carrying out the same procedure as in Example 3 using barium ferrite magnetic powder having a plate ratio of 3, a coercive force of 580 oersted, a saturation magnetization of 57 emu/gs, and an average particle size of 0.1 μm.

[Comparative Example 12] The same procedure as in Example 3 was carried out using metal iron magnetic powder having an acicular ratio of 3, a coercive force of 670 oersted, a saturation magnetization of 125 emu/g, and an average particle size of 0.2 μm.
Get the disc.

〔Characteristic〕

Regarding the magnetic tapes of Example 1 and Comparative Examples 3 and 4.5 above, the magnetic tapes were placed in an atmosphere with a temperature of 40°C and a humidity of 8096RH, and how the FM output of the magnetic tapes changed over time. The results of the investigation are shown in Figure 1.

According to this, the FM output of the example has a small decrease, whereas the FM output of the comparative example has sharply decreased in a short period of time, and the magnetic recording medium of the present invention has magnetic characteristics. It can be seen that there is little deterioration in , and the durability is high.

Further, for the floppy disks of Example 3 and Comparative Examples 8, 9, 10, 11, and 12, an FM signal was input and the frequency characteristics of the reproduced output were investigated, and the results are shown in FIG.

According to this, the magnetic recording medium of the present invention has a high reproduction output in the high-frequency region, whereas the comparative example has a low reproduction output in the high-frequency region, and the magnetic recording medium of the present invention is suitable for high-density recording. I can see that it is something.

FIG. 3 shows the results of examining the C/N frequency characteristics of the magnetic tape sheets ζ of Examples 1 and 2 and Comparative Examples 1 and 2.3.

According to this, the C/N of the present example is high in the high frequency region, whereas the C/N of the comparative example is low in the high frequency region, and the magnetic recording medium of the present invention is suitable for high-density recording. It turns out that it is suitable.

Further, FIG. 4 shows the results of recording 5 MHz FM signals on the magnetic tapes of Examples 1 and 2 and Comparative Examples 6 and 7 and examining their input/output characteristics.

According to this, it can be seen that the magnetic tape of the present example has good input/output characteristics, but the magnetic tape of the comparative example has poor input/output characteristics.

〔effect〕

It has good C/N, output, and input/output characteristics in the high frequency region, and is highly durable with little deterioration in magnetic properties.

Further, a magnetic recording medium with good vertical alignment can be obtained without special magnetic field alignment treatment, and can be manufactured with high productivity.

BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1 to 4 are graphs showing the characteristics of magnetic recording media. 11 絽 To exist kikon (+)

Claims (1)

[Claims] A hexagonal ferrite magnetic powder with a plate ratio of 5 or more and a coercive force of 600 Oe or less, and a ferromagnetic powder with an acicular ratio of 4 or more, a saturation magnetization of 100 emu/g or more, and a coercive force of 700 Oe or less are magnetic. A magnetic recording medium, wherein the ferromagnetic powder is contained in a layer in an amount of 30 parts by weight or less relative to 70 to 100 parts by weight of the hexagonal ferrite magnetic powder.