JPS61233418A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain the title medium having excellent output and C/N in the high-frequency region and also having excellent traveling property and orientation property by jointly using hexagonal ferrite magnetic powder and acicular ferromagnetic powder. CONSTITUTION:Hexagonal ferrite magnetic powder having >=5 squareness ratio and >=600Oe coercive force is selected and ferromagnetic powder having >=4 acicular ratio, >=100emu/g saturation magnetization and >=700Oe coercive force is selected. Less than 30pts.wt. ferromagnetic powder is used with 70-100pts.wt. hexagonal ferrite magnetic powder. More preferably, about 70-95wt% hexagonal ferrite magnetic powder is used with about 30-5wt% ferromagnetic powder. In addition to the mixing ratio, the coercive force of the hexagonal ferrite magnetic powder is preferably regulated to about 700-1500Oe and the coercive force of the ferromagnetic powder is adjusted to about 700-1500Oe to improve the C/N and reproducing output in the high-frequency region.

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 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 proposed 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. While researching and developing mixed magnetic recording media, we selected hexagonal ferrite magnetic powder with a plate ratio of 5 or more and a coercive force of 600 Oe or more, and also selected ferromagnetic powder. The acicular ratio is 4 or more, and the saturation magnetization is 100 emu/
g or more and has a coercive force of 700 Oe or more, 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. It has been found that if the amount is 30 parts by weight or less, a magnetic recording medium with little change in magnetic properties over time, good high frequency properties, high density, and high output can be obtained.

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, and even more preferably the proportion of ferromagnetic powder is about 30% to 5% by weight relative to about 70% to 95% by weight of hexagonal ferrite magnetic powder. It is desirable that

Furthermore, it is desirable that the ratio of the hexagonal ferrite magnetic powder and the ferromagnetic powder be as described above, not only from the viewpoint of the magnetic properties but also from the viewpoint of the C/N and reproduction output characteristics. . In order to improve the characteristics of C/N and reproduction output in this high frequency range, it is necessary not only to improve the ratio of hexagonal ferrite magnetic powder and ferromagnetic powder, but also to increase the coercive force of the hexagonal ferrite magnetic powder to 600 Oe or more. It is preferable that the ferromagnetic powder has a saturation magnetization of 100 emu/g or more and a coercive force of 700 to 1500 oersteds, and even more preferably about 700 to 1500 oersteds. be.

In addition, 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, the orientation can be improved. In addition, the C/N characteristics are also improved.

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 7, coercive force 680 oersted, saturation magnetization 57 emu)
/ g, average particle size 0.2 μm) 85 parts by weight, metal iron magnetic powder (acicular ratio 6, coercive cuff 50 oersted, saturation magnetization 120 emu/g, average particle size 0.2 μm) 15 parts by weight, binder 25 parts by weight, 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, 3 parts by weight of solvent.
00 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 1 inch width. to obtain magnetic tape.

[Example 2] In Example 1, a barium ferrite magnetic powder with a plate ratio of 7, a coercive force of 860 Oersted, a saturation sensitivity of 57 emu/g, and an average particle size of 0.2 μm and an acicular ratio of 6, a coercive force of 1200 Oersted, and a saturation magnetization A magnetic tape was obtained in the same manner using metal iron magnetic powder of 120 emu/g and an average particle size of 0.2 μm.

[Example 3] A magnetic tape was obtained by carrying out the same procedure as in Example 1 using barium ferrite magnetic powder having a plate ratio of 9, a coercive force of 680 oersted, a saturation magnetization of 57 emu/gs, and an average particle size of 0.2 μm. .

[Example 4] The same procedure as in Example 1 was repeated 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 to obtain a magnetic tape.

[Example 5.6] In Example 1.4, instead of using magnetic tape, 3.5
Punch out a piece with a diameter of 1 inch to obtain a floppy disk.

[Comparative Examples 1 to 4] In Example 1, the amounts of barium ferrite magnetic powder and metal iron magnetic powder were changed to 0 parts by weight and 100 parts by weight (Comparative Example 1)
, 25 parts by weight and 75 parts by weight (Comparative Example 2) 50 parts by weight and 5 parts by weight
The same procedure was carried out using 0 parts by weight (Comparative Example 3), 65 parts by weight, and 35 parts by weight (Comparative Example 4) to obtain magnetic tapes.

[Comparative Example 5] In Example 1, the plate ratio was 3, the coercive force was 680 Oe, the saturation magnetization was 57 emu/gs, and the average grain size was 0.2.
A magnetic tape is obtained in the same manner using μm barium ferrite magnetic powder.

[Comparative Example 6] In Example 1, the plate ratio was 7, the coercive force was 450 oersted, the saturation magnetization was 57 ernu/gs, and the average grain size was 0.2.
μm barium ferrite magnetic powder, acicular ratio 6, coercive force 5
The same procedure was carried out using metal magnetic powder of 80 oersted, saturation magnetization of 120 emu/g, and average particle size of 0.2 μm.
Get magnetic tape.

[Comparative Examples 7 to 10] In Comparative Examples 1 to 4, instead of using magnetic tape, 3.5
Punch out a piece with a diameter of 1 inch to obtain a floppy disk.

〔Characteristic〕

The input/output characteristics of the magnetic tapes of Example 1.2 and Comparative Example 1.6 at a recording frequency of 5 MHz are as shown in FIG. 1.

According to this example, even if the recording voltage is high, the reproduction output is high, that is, the amount of barium ferrite magnetic powder is about 70% by weight or more, the coercive force of the barium ferrite magnetic powder is about 600 Oe or more, and the needle It can be seen that good input/output characteristics can be obtained by setting the saturation magnetization of the ferromagnetic powder to 10100 e/g or more and the coercive force to 700 Oe or more.

Furthermore, when the frequency characteristics of C/N at a recording voltage of 3.5 V are investigated, they are as shown in FIG.

According to this, the C/N of this example is large even in the high frequency range, that is, by setting the amount of barium ferrite magnetic powder to about 70% by weight or more and the plate ratio of barium ferrite magnetic powder to 5 or more. It can be seen that the output is improved over a wide frequency band.

Further, when examining the coefficient of dynamic friction of the magnetic tape, it is as shown in FIG.

According to this, the coefficient of dynamic friction tends to gradually decrease as the amount of barium ferrite magnetic powder increases, but when the amount of barium ferrite magnetic powder is about 70% by weight or more, it becomes even smaller, and good running performance is achieved. You can see what you can get.

Furthermore, when examining the modulation of the above floppy disk, the modulation of Example 5 was 2.3%.
, it was only 1.8% in Example 6, 11.5% in Comparative Example 7, and 8.7% in Comparative Example 8.
, 5.3% for Comparative Example 9 and 3.5% for Comparative Example 10, indicating that the floppy disk of this example has high performance with little output fluctuation. In other words, since acicular ferromagnetic powder is easily subject to mechanical orientation during the coating process, if there is a large amount of acicular ferromagnetic powder, slitting it into a disk shape will likely cause differences in orientation in the circumferential direction, resulting in large output fluctuations. It is desirable that the barium ferrite magnetic powder is about 70% by weight or more.

〔effect〕

Good output and C/N in high frequency range,
Moreover, a product with good running properties can be obtained.

Furthermore, a magnetic recording medium with good orientation can be obtained without special magnetic field orientation treatment.

[Brief explanation of drawings]

1 to 3 are graphs showing the characteristics of magnetic recording media. Patent applicant: Victor Company of Japan Co., Ltd. Agent: Katsu Uko
, - leading edge tε(7) 1 mouthffiJ-2LgCMji)

Claims (1)

[Claims] A hexagonal ferrite magnetic powder with a plate ratio of 5 or more and a coercive force of 600 Oe or more, 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 more 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.