JPS61233419A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain the title medium having an excellent producing output in the high-frequency region and an excellent erasing characteristic and further having excellent durability by jointly using hexagonal ferrite magnetic powder and acicular ferromagnetic powder. CONSTITUTION:The hexagonal ferrite magnetic powder having <=5 squareness ratio and <=600Oe coercive force is selected and the ferromagnetic powder having <=4 acicular ratio, 60-100emu/g saturation magnetization and <=700Oe coercive force is selected. Less than 80pts.wt. ferromagnetic powder is used with 20-100pts.wt. hexagonal ferrite magentic powder. More preferably, about 20-95wt% hexagonal ferrite magnetic powder is used with about 80-5wt% ferromagnetic powder. In addition to the mixing ratio, the coercive force of the hexagonal ferrite magnetic powder is preferably regulated to about 400-600Oe and the coercive force of the ferromagnetic powder is adjusted to about 500-700Oe to improve the frequency characteristic.

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, acicular γ-Fe! 0
! The main method is the so-called horizontal magnetic recording method, in which a magnetic paint containing 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.

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 proposed9.
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 that a combination of hexagonal ferrite magnetic powder and ferromagnetic powder, such as barium ferrite magnetic powder, strontium 7-elite magnetic powder, calcium ferrite magnetic powder, lead ferrite magnetic powder, or substituted barium ferrite magnetic powder, be mixed together. While conducting research and development of 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 also selected ferromagnetic powder as has an acicular ratio of 4 or less and a saturation magnetization of 60~too em
u/g and has a coercive force of 700 Oe or less, and the ratio of the hexagonal ferrite magnetic powder with the above characteristics and the ferromagnetic powder with the above characteristics is 20 to 100 parts by weight of the former to 100 parts by weight of the latter. If the amount is 80 parts by weight or less, it is possible to obtain a high-density, high-output magnetic recording medium with little change in magnetic properties over time (for example, little decrease in playback output due to change over time) and good high-frequency properties. I found it.

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 reproduction output will drop significantly due to changes over time, and the reproduction output in the high frequency region will also decrease significantly. The ratio of ferromagnetic powder to ~100% by weight is 80% by weight or less, and even more preferably the ratio of hexagonal ferrite magnetic powder to approximately 20 to 95% by weight and ferromagnetic powder to approximately 80 to 5% by weight. It is desirable that

Furthermore, in order to improve the frequency characteristics, not only the ratio of the hexagonal ferrite magnetic powder and the ferromagnetic powder but also the coercive force of the hexagonal ferrite magnetic powder should be 600 Oe or less, more preferably about 400 to 600 Oe. It is desirable that the ferromagnetic powder has a saturation magnetization of 60 to 10,100 e/g and a coercive force of 700 Oe or less, more preferably about 500 to 700 Oe.

Furthermore, it is desirable that the coercive force of the hexagonal ferrite magnetic powder and the ferromagnetic powder be as described above not only from the viewpoint of improving frequency 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 magnetic paint can be The dispersibility of the magnetic layer is improved, random orientation can be obtained, high output can be achieved in a high frequency region, and the durability of the magnetic layer is 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 5, coercive force 570 Oe, saturation magnetization 57 emu/
g, average particle size 0.1 μm) 60 parts by weight, Co-coated Felon magnetic powder (acicular ratio 4, coercive force 650 Oe, saturation magnetization 85 emu/g, average particle size 0.2 μm)
A magnetic paint was prepared by thoroughly cross-dispersing a mixture of 40 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, and 300 parts by weight of solvent. After adding a hardening agent to this magnetic paint, it is applied onto a non-magnetic substrate such as polyethylene terephthalate.
After drying, it is calendered and slit into i inch width to obtain a magnetic tape.

[Examples 2 to 5] In Example 1, the amounts of barium ferrite magnetic powder and Co-coated Fet's magnetic powder were changed to 20 parts by weight and 80 parts by weight (Example 2), and 40 parts by weight and 60 parts by weight. Parts by weight (Example 3
), 80 parts by weight and 20 parts by weight (Example 4), and 95 parts by weight and 5 parts by weight (Example 5) to obtain magnetic tapes.

[Example 6] In Example 1, the acicular ratio was 4, the coercive force was 580 Oe, the saturation magnetization was 85 emu/gs, and the average particle size was 0.2 μ.
A magnetic tape is obtained in the same manner using Co-coated Fe1rs magnetic powder.

[Example 7] A magnetic tape is obtained by carrying out the same procedure as in Example 6 using barium ferrite magnetic powder having a plate ratio of 3, a coercive force of 570 Oe, a saturation magnetization of 57 emu/g, and an average particle size of 0.1 μm.

[Example 8.9] In Example 4.5, instead of using magnetic tape, 3.5
Punch out a piece with a diameter of 1 inch to obtain a floppy disk.

[Comparative Example 1] A magnetic tape was obtained in the same manner as in Example 1 except that 5 parts by weight of the barium ferrite magnetic powder and 95 parts by weight of the CO-coated Fe2rs magnetic powder were used.

[Comparative Example 2] In Example 1, the plate ratio was 9, the coercive force was 570 Oe, the saturation magnetization was 57 emu/g, and the average particle size was 0.1 μ.
m barium ferrite magnetic powder, acicular ratio 4, coercive force 88
0 oersted, saturation magnetization 85 emu/g, average particle size 0
．． A magnetic tape is obtained in the same manner using 2 μm of Co-coated Fears magnetic powder.

[Comparative Example 3] In Example 1, the plate ratio was 10, the coercive force was 570 Oe, the saturation magnetization was 57 emu/gs, and the average grain size was 0.
1 μm barium ferrite magnetic powder, acicular ratio 4, coercive force 1250 Oe, saturation magnetization 85 emu/g,
A magnetic tape is obtained by carrying out the same procedure using CO-coated Fetus magnetic powder having an average particle size of 0.2 μm.

[Comparative Example 4] In Example 1, the plate ratio was 15, the coercive force was 570 Oe, the saturation magnetization was 57 emu/gs, and the average grain size was 0.
A magnetic tape is obtained by carrying out the same procedure using 1 μm barium ferrite magnetic powder.

[Comparative Example 5] In Example 1, a metal magnetic powder with an acicular ratio of 4, a coercive force of 1200 Oe, a saturation magnetization of 115 emu/g, and an average particle size of 0.2 μm was used instead of the CO-adhered Fears magnetic powder. Perform the same procedure to obtain a magnetic tape.

[Comparative Example 6] In Comparative Example 1, instead of making a magnetic tape, a floppy disk was punched out with a diameter of 3.5 inches.

〔Characteristic〕

The frequency characteristics of the magnetic tapes on each side at recording voltages of 3 and 5 V were investigated as shown in FIG.

According to this, it can be seen that the reproduction output of this example is much higher in the high frequency region. That is, the proportion of the barium ferrite magnetic powder is 20% by weight or more, the plate ratio of the barium ferrite magnetic powder is 5 or less, and the saturation magnetization of the ferromagnetic powder is 60%.
~100 emu/g, and the coercive force is 7
By choosing one that is less than or equal to 00 Oersteds,
This makes it possible to further improve reproduction output in the high frequency region.

In addition, when examining the erasing characteristics of the magnetic tape on each side, the second
As shown in the figure.

According to this, the coercive force of barium ferrite magnetic powder is 6
It can be seen that good erasing characteristics can be obtained by setting the coercive force of the ferromagnetic powder to 700 Oe or less.

In addition, after recording the color par signal on the magnetic tape on each side, the time required for the output to completely go down (still out) by playing back the still image is determined, and the plate ratio of the barium ferrite magnetic powder and the still time are calculated. When we examine the relationship between the two, we find that it is as shown in Fig. 3.

According to this, the plate ratio of barium ferrite magnetic powder is
It can be seen that this has a large effect on the durability of the magnetic layer. In other words, it can be seen that when the acicular ratio of the ferromagnetic powder is 4 or less and the plate ratio of the barium ferrite magnetic powder is 5 or less, the still time is long and the magnetic layer is highly durable.

Moreover, when examining the modulation of the above floppy disk, the modulation of Example 8 is 2.1%.
, is small at 1.5% in Example 9, while it is 12.1% in Comparative Example 6, and this example has high performance with little output fluctuation. In other words, the proportion of the barium ferrite magnetic powder was set to 20% by weight or more to minimize the defects caused by the acicular ferromagnetic powder, which is susceptible to mechanical orientation during the coating process, and to minimize output fluctuations.

〔effect〕

Good playback output in the high frequency range and good erasing characteristics.
Furthermore, a product with high durability can be obtained.

[Brief explanation of drawings]

1 to 3 are graphs showing the characteristics of magnetic recording media. Patent Applicant: Victor Company of Japan 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 60 to 100 emu/g, and a coercive force of 700 Oe or less. A magnetic recording medium, wherein the ferromagnetic powder is contained in a magnetic layer in an amount of 80 parts by weight or less relative to 20 to 100 parts by weight of the hexagonal ferrite magnetic powder.