JPS61202331A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve an erasing characteristic by specifying the ratio of the ferromagnetic powder to be added to the hexagonal ferrite magnetic powder contained in a magnetic layer at <=30pts.wt. by 70-100pts.wt. said ferrite magnetic powder. CONSTITUTION:The hexagonal ferrite magnetic powder having <=5 planar ratio and <=600 oersted coercive force is used and the ferromagnetic powder having <=4 acicular ratio, <=100emu/g satd. magnetization and <=700 oersted coercive force is used. The ratio of the hexagonal ferrite magnetic powder and the ferromagnetic powder is specified at <=30pts.wt. the latter by 70-100pts.wt. the former. The magnetic recording layer which has the decreased deterioration of the magnetic characteristics with lapse of time, the good erasing characteristic, good high-frequency characteristic, high density and high output is thus obtd.

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, magnetic recording media have been produced by coating a magnetic paint containing acicular γ-Fee's magnetic powder on a non-magnetic substrate, and then oriented the magnetization in the in-plane longitudinal direction by an orientation process 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
00 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 an FD Jltlf binder. Proposal (Unexamined Japanese Patent Publication No. 1983-
No. 203625).

In other words, the technical idea of this proposal is that simply using ferromagnetic powder and hexagonal ferrite magnetic powder would result in a decrease in magnetic properties due to poor dispersibility of the magnetic paint. It is stated that if this configuration is adopted, the dispersibility of the magnetic coating material will be improved, and thus a magnetic recording medium with good magnetic properties can 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 researching and developing magnetic recording media, we selected hexagonal ferrite magnetic powder with a platelet ratio of 5 or less and a coercive force of 600 Oe or less, and ferromagnetic powder with The acicular ratio is 4 or less, and the saturation magnetization is 100. emu/
g or more and has a coercive force of 700 Oe 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, improving reproduction output in the high frequency range and achieving high-density recording. In addition, although the horizontal magnetization component of the acicular ferromagnetic powder can be effectively used and the reproduction output in the low frequency range is improved, the relative amount of the ferromagnetic powder to the hexagonal ferrite magnetic powder is If the amount is too large, the deterioration of the magnetic properties will be severe, for example, the FM output will decrease significantly due to aging, and the reproduction output in the high frequency region will also decrease significantly. The proportion of ferromagnetic powder is 30% by weight or less based on ~100% by weight, more preferably about 70% to 95% by weight of hexagonal ferrite magnetic powder, and about 30% to 5% by weight of ferromagnetic powder based on the weight%. It is desirable that the ratio be as follows.

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 range, it is important to not only adjust the ratio of hexagonal ferrite magnetic powder to ferromagnetic powder, but also to ensure that the coercive force of the hexagonal ferrite magnetic powder is 600 Oe or less, more preferably approximately 400 to 600 Oe, and the saturation magnetization of the ferromagnetic powder is 1
It is desirable that the coercive force is at least 0.0100 e/g and at most 700 Oe/g, more preferably from 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 erasing characteristics.

In addition, by using a hexagonal ferrite magnetic powder whose platelet ratio is 5 or less, preferably about 1 to 5, and a ferromagnetic powder whose acicular ratio is 4 or less, preferably about 1 to 4, the orientation can be improved. This results in improved output power in the high frequency range.

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 3, coercive force 550 Oe, saturation magnetization 57 emu/
g, average particle size 0.0 Bpm) 85 parts by weight, metallic iron magnetic powder (acicular ratio 4, coercive force 680 Oe, saturation magnetization 12
5 emu/g, average particle size 0.2 μm) 15
9 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,
A magnetic paint is prepared by thoroughly cross-dispersing a mixture of 300 parts by weight of a solvent, a curing agent is added to the magnetic paint, and the paint is applied onto a non-magnetic substrate such as polyethylene terephthalate. After drying, it is calendered and slit to -inch width. 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] In Example 1, the acicular ratio was 10, the coercive force was 1000 Oe, the saturation magnetization was 125 emu/g, and the average particle size was 02 μm.
A magnetic tape is obtained by carrying out the same procedure using metallic iron magnetic powder.

[Comparative Example 2] In Example 1, the acicular ratio was 4, the coercive force was 1400 Oe, the saturation magnetization was 125 emu/g, and the average particle size was 0.2 μm.
A magnetic tape is obtained by carrying out the same procedure using metallic iron magnetic powder.

[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 65 parts by weight and the metal iron magnetic powder was 35 parts by weight.
Get magnetic tape.

[Comparative Example 6] In Example 1, the plate ratio was 3, the coercive cuff was 00 Oe, the saturation magnetization was 57 emu/g, and the average particle size was 0.08 pm.
A magnetic tape is obtained by carrying out the same procedure using barium ferrite magnetic powder.

[Comparative Example 7] In Example 1, the plate ratio was 3, the coercive force was 850 Oe, the saturation magnetization was 57 emu/g, and the average particle size was 0608.
A magnetic tape is obtained in the same manner using μm barium ferrite magnetic powder.

[Comparative Examples 8 to 10] According to Comparative Examples 3 to 5, instead of making a magnetic tape by slitting it to a width of i inch, a floppy disk was punched to a diameter of 5.25 inches.

〔Characteristic〕

Regarding the magnetic tapes of Example 1.2 and Comparative Examples 3 and 4.5, the magnetic tapes were heated at a temperature of 40°C and a humidity of 8096R.
By placing the magnetic tape in an atmosphere of H and examining how the FM output of the magnetic tape changes over time, we find that
As shown in FIG.

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, when an FM signal was input to the floppy disks of Example 3 and Comparative Examples 8, 9, and 10 and the frequency characteristics of the reproduced output were examined, the results were as shown in FIG.

According to this, the reproduction output of the example is high in the high frequency region, whereas the reproduction output 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 is something.

Further, when the C/N frequency characteristics of the magnetic tapes of Example 1.2 and Comparative Examples 4, 5, and 6.7 were examined, the results were as shown in FIG.

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 capable of high-density recording. It is suitable.

Further, when a 4 MHz FM signal was recorded on the magnetic tapes of Example 1.2 and Comparative Example 3.4, and the erasing characteristics thereof were examined, the results are as shown in FIG.

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

〔effect〕

It has a high output in the high frequency range, is highly durable with little deterioration in magnetic properties, and also has good erasing 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 explanation of the drawing]

1 to 4 are graphs showing the characteristics of magnetic recording media. Patent applicant: Victor Japan Co., Ltd.

Claims (1)

[Claims] A hexagonal ferrite magnetic powder with a plate ratio of 5 or less and a coercive force of 600 Oe or less, and a ferromagnetic powder with an acicular ratio of 4 or less, 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.