JPH0349025A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve output and C/N in submicron region by specifying the ratio of the half width of differential curve to the coercive force of the saturation magnetization hysteresis curve, the squareness ratio in the same direction as that of head traveling, the ratio of particle size to particle thickness, and the particle size of the magnetic powder. CONSTITUTION:A magnetic coating material is prepared by kneading the magnetic powder with additives and an org. binder, and then applied on a nonmagnetic body to obtain the magnetic recording medium. The ratio dHc/Hc, wherein Hc is the coercive force determined by the saturation magnetization hysteresis curve of this magnetic recording medium and dHc is the half width of the differential curve of the saturation magnetization hysteresis curve at H=Hc, is specified to <0.5, and the squareness ratio of the saturation magnetization hysteresis curve in the same direction as that of the traveling direction of a head is specified to >0.7. The particle size to thickness ratio of the magnetic powder particles is specified to 1-5 and the particle size to 300-700 A. The magnetic powder of plate-type particles above described is used for the magnetic recording layer.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is particularly suited for use in video floppy disks, etc., which require high-density recording in the submicron region. The present invention relates to type magnetic recording media.

BACKGROUND OF THE INVENTION Magnetic recording has traditionally been developed using a longitudinal magnetic recording method that uses in-plane magnetization of a magnetic recording medium. Most of the magnetic tapes currently in use are magnetic tapes based on this longitudinal recording method.

At present, magnetic materials such as acicular iron oxide and metal are mainstream as magnetic materials constituting the media, and alumina is used to increase coating strength and polish the magnetic head, and to lower electrical resistance and runnability. Carbon is added to improve running performance and lubricant is added to improve runnability and durability, and these materials are uniformly dispersed in an organic binder to obtain a magnetic film.

-a. In longitudinal recording, in order to increase the output, the magnetic powder in the coating film is required to be oriented in the head-medium traveling direction. In the longitudinal recording method, the C/N increases during high-density recording as the degree of longitudinal orientation of the magnetic powder in the coating film increases, so the prior disclosed technology attempts to increase the longitudinal orientation. For example, JP-A-62-172533
No. 1, JP-A-62-219332, JP-A-62
-298927.

However, it is known that the longitudinal recording method must overcome self-demagnetization loss during high-density recording, and therefore increasing the coercive force of the medium is an essential condition for high-density recording. However, it is technically difficult to increase the coercive force of the current acicular iron oxide and metal magnetic powder even higher than this, and there are also issues with the heads that can write sufficiently on high coercive force media. be.

It is well known that a perpendicular magnetic system has been proposed as a method to solve this problem of longitudinal recording. For example,
Literature includes Shiraki, Nakamura, and Iwasaki, Journal of the Japanese Society of Applied Magnetics, Vol. 11 (1987) P2O3-114. In perpendicular recording, the higher the density of recording, the smaller the self-demagnetization loss, and practical research is being conducted in various places as the ultimate magnetic recording method. As prior disclosed technology, Japanese Patent Application Laid-Open No. 60-1
There are publications such as No. 32183.

There is also a technical report that uses hexagonal plate-shaped barium ferrite magnetic powder and applies it to a perpendicular recording system.

For example, JP-A-60-211628, JP-A-60
-209928, JP 60-212817, JP 61-230621, JP 62-6
There is a publication No. 0122.

Problems to be Solved by the Invention However, in the current development of coated magnetic recording media, it is not always possible to improve the media characteristics even if a plate-shaped magnetic powder is simply applied as a paint, as disclosed in the prior art. It is hard to say that it is good.

Specifically, it has had the problem that it cannot necessarily be said to be superior to the output and C/N of submicron recording wavelengths of commercially available metal tapes.

! Means for Solving the Problems In order to solve the above problems, the magnetic recording medium of the present invention has the following features:
dH calculated from the coercive force (Hc) obtained from the saturation magnetic hysteresis curve of the magnetic recording medium in the magnetic recording layer and the half-value width (dHc) of the fine powder curve of the saturation magnetic hysteresis curve near H-Hc.
The value of c/Hc is 0.5 or less, the squareness ratio in the same direction as the head running direction in the saturation magnetic hysteresis curve of the magnetic recording medium and the magnetic head in the running direction is 0.7 or more, and at the same time, the grain size and The ratio of particle thickness is 1 to 5, and the particle size is 300 to
The structure is characterized in that the magnetic recording layer is provided with plate-shaped magnetic powder having a thickness of 700 angstroms.

Operation The present invention, with the above-described configuration, has good output and C/N in the submicron region, and can achieve a C/N that cannot be achieved with the current combination of a coating type medium and a ring head. As for its effects, the above-mentioned structure can reduce the noise generated by the recording medium, and since the particles are ultra-fine, the deposition filling rate of magnetic powder can be increased compared to conventional coated media, and the actual amount of magnetization can be improved. Furthermore, it is presumed that the magnetization transition occurs abruptly because the magnetization reversals occur all at once.

EXAMPLE A magnetic recording medium according to an example of the present invention will be described below.

Example 1 The following components were adjusted as a coating composition, and a pressure kneader,
Using a double planetary mixer, disper, etc.
Mixing and dispersion was performed to produce a magnetic paint.

・Plate magnetic powder (barium ferrite with a hexagonal crystal structure containing Co-Ti-Zn as a substituent element) (Plate diameter 370 mm, plate thickness 140 mm, coercive force 9500e, saturation magnetization 63 emu/g) 200
Part/Vinyl chloride polymer ・・・・・・ 15
Part/Polyurethane 1
Part 5, carbon...
Part 4, alumina...8
Part/Lubricant 2
Part/Solvent Toluene...18
0 parts MEK 180 parts Hardening agent 12
After filtering the obtained paint, the blade gap 3
Coating was performed using a 0 μm applicator. A polyethylene terephthalate film with a thickness of 14 μm was used as the substrate, and immediately after the magnetic paint was applied, it was oriented in the running direction of the substrate using a solenoid coil that emits a magnetic flux of 5000 Gauss. Next, calender treatment (80°C 130kg/c
b), and a curing treatment was performed at 60°C for 124 hours. The magnetic field of the obtained sample was measured using a vibrating sample magnetometer (maximum magnetic field: 10 KOe).

Example 2 In Example 2, the plate-shaped magnetic powder of Example 1 was changed to magnetic powder whose surface was spinel-coated with barium ferrite, and the coating material and tape were prepared in the same manner. The particles have a plate diameter of 450 and a plate thickness of 1.
50 people, coercive force 9000e, saturation magnetization 68 emu/g
This was the characteristic.

Comparative Example 1 Comparative Example 1 followed Example 1 except that barium ferrite magnetic powder belonging to the 60,000-crystal system was used, which had a manufacturing loft different from that of the plate-shaped magnetic powder of Example 1. Particle size is 800, plate thickness is 1
30 people, coercive force 9100e, saturation magnetization 64 emu/g
Met.

Comparative Example 2 Comparative Example 2 has a plate diameter of 720 particles, a plate thickness of 200 particles, and a coercive force of 8 particles, which have a different manufacturing loft from the particles of Example 2 with a plate diameter of 450 particles.
500e and a saturation magnetization of 69 emu/g were used in accordance with Example 2 to form a tape.

Comparative Examples 3 and 4 Comparative Examples 3 and 4 were formed into tapes in the same manner as in Example 1 and 2, except that the orientation treatment was not performed.

Comparative Example 5.6 Comparative Example 5 was the same as in Example 1 except that the plate diameter was 690 mm, the plate thickness was 130 mm, the coercive force was 9200 e, and the saturation magnetization was 53 emu/g. 6 is the plate-shaped magnetic powder used in Example 2, with a plate diameter of 680,
A tape was produced in accordance with Example 2, except that the plate thickness was 120 mm, the coercive force was 8800 e, and the saturation magnetization was 61.9 parts mu/g.

Comparative Example 7.8 In Comparative Example 7.8, the plate-shaped magnetic powder used in Example 1.2 was prepared with a plate diameter of 1200 mm, a plate thickness of 300 mm, and a coercive force of 9 mm.
150 e, saturation magnetization 62.2e+au/g, plate diameter i
oo.

Person, board thickness 200 persons, coercive force 9150e, saturation magnetization 66.
Tape-forming was carried out according to Example 1.2 except that the amount was 8 parts mu/g.

Comparative example 9 Comparative Example 9 was a commercial MII-MP tape.

One part of the sample obtained in this way was slit into a 2-inch width, and the electromagnetic conversion characteristics were measured at a relative speed of 3.50 m/sec.
c, metal laminated head (gap length 0.20 μm,
The measurement was performed using a track width of 20 μm and a number of windings of 25 times. The recording frequency required for measurement was 0.5.1.2.3.5.
It is 5.7.8MHz.

The magnetic properties of the samples were measured at a maximum magnetic field of 10 KOe and a sweep rate of 3 minutes/10 KOe. In addition, the surface roughness of the sample greatly affects the output during short wavelength recording, so
It was measured using an optical non-contact surface roughness meter.

These results are summarized in Table 1.

The CN ratio of the reproduced signal shows the value at the optimum recording current, and is shown as a relative value based on the CN ratio of Comparative Example 9. The arrow represents the longitudinal direction of the medium, and the upper represents the thickness direction of the medium.

As is clear from Table 1, the magnetic recording medium of the present invention exhibits superior tape characteristics at submicron recording wavelengths compared to coated metal tapes, and is useful as a high-density, large-capacity magnetic medium. .

In the examples, the plate-shaped magnetic powder was Co-Ti-Zn!
In Example 2, barium ferrite was used as the surface of barium ferrite. Although a material coated with an excessive amount of spinel ferrite was used, the present invention is not limited to this.

Effects of the Invention As described above, the magnetic recording medium of the present invention has a coercive force (Hc) obtained from a saturation magnetic hysteresis curve in the running direction of the magnetic recording medium and a magnetic head, and a saturation magnetic hysteresis curve near H=Hc. d H calculated from the half width (dHc) of the differential curve of
The value of c/Hc is 0.5 or less, the squareness ratio in the same direction as the running direction in the saturation magnetic hysteresis curve in the direction of the magnetic recording medium and the magnetic head is 0.7 or more, and the particle size and particle thickness are By providing the magnetic recording layer with plate-shaped magnetic powder having a ratio of 1 to 5 and a grain size of 300 to 700 angstroms, the tape characteristics can be surpassed by commercially available metal tapes. The magnetic recording medium of the present invention can be used for low-cost, large-capacity information recording, and greatly contributes to improving the performance of video equipment and memory equipment, making it an extremely useful invention.

Claims (3)

[Claims] (1) A magnetic recording medium obtained by preparing a magnetic paint by kneading plate-shaped magnetic powder and an additive/organic binder, and then applying the paint onto a non-magnetic substrate,
The value of dHc/Hc calculated from the coercive force (Hc) obtained from the saturation magnetic hysteresis curve of the magnetic recording medium and the half-value width (dHc) of the fine powder curve of the saturation magnetic hysteresis curve near H=Hc is 0.5. The squareness ratio in the same direction as the head running direction in the saturation magnetic hysteresis curve in the running direction of the magnetic recording medium and the magnetic head is 0.7 or more, and the ratio of grain size to grain thickness is 1 to 5. 1. A magnetic recording medium comprising, in a magnetic recording layer, plate-shaped magnetic powder having a particle size in the range of 300 to 700 angstroms. (2) The magnetic recording medium according to claim (1), wherein the plate-shaped magnetic powder has a crystal structure belonging to the 60,000 crystal system. (3) The plate-shaped magnetic powder has a magnetoplumbite-type structure R
2. The magnetic recording medium according to claim 1, wherein the magnetic recording medium has an excessive spinel structure in addition to the regular stacking of blocks and S blocks.