JPH0467424A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve tape characteristics by specifying the ratio between the coercive force obtd. form the residual magnetization curve in a traveling direction and the half-value width of the differential curve of the residual magnetization curve to be <=0.5 and specifying the squareness ratio in the satd. magnetization curve measured in the traveling direction to be >=0.7. CONSTITUTION:The value of dHr/Hr calculated from the coercive force (Hr) obtd. from the residual magnetization curve of the magnetic recording medium in the magnetic recording layer and the half-value width (dHr) of the differential curve of the residual magnetization curve near H=Hr is <=0.5 and the square ness ratio in the same direction as the head traveling direction of the satd. magnetization curve in the traveling direction of the magnetic recording medium and the magnetic head is >=0.7. Then, the noises generated from the recording medium are decreased and since the magnetic powder is superfine particles, the volumetric packing rate of the magnetic powder can be increased to the value larger than that of the conventional coating type media and the effective magnetization quantity is improved. Further, magnetization inversion takes place simultaneously, the transfer of the magnetization takes place rapidly. The output in a submicron region is improved together with C/N in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is a coating type magnetic material with particularly excellent C/N for use in video/Frombie disks that require high-density recording in the submicron region. It is related to 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 use this longitudinal recording method.

At present, magnetic materials such as acicular iron oxide and metal are mainstream as the magnetic materials that make up the media.Also, alumina is used to increase coating strength and polish the magnetic head, and to lower electrical resistance and improve 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.

Generally, in longitudinal recording, in order to increase the output, it is required that the magnetic powder in the coating film be oriented in the head-medium running direction. In the longitudinal recording method, attempts have been made to increase the degree of longitudinal orientation because the greater the degree of longitudinal orientation of the magnetic powder in the coating film, the greater the C/N during high-density recording.

Prior disclosed technologies include JP-A-62-172533, JP-A-62-219332, and JP-A-62-2.
This is shown in JP-A No. 98927 and the like. 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 problems with the heads that can write sufficiently on high coercive force media. be.

It is well known that perpendicular magnetic recording has been proposed as a method for solving the problems of longitudinal recording.

For example, the literature includes Shiraki, Nakamura, and Iwasaki, Journal of the Japan Society of Applied Magnetics, Vol. 11 (1987), p. 109-114.

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 an earlier disclosed technology, Japanese Patent Application Laid-open No. 6
There are publications such as No. 0132183.

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 are publications such as No. 0122.

Problems to be Solved by the Invention However, in the current development of coating-type magnetic recording media, simply applying plate-shaped magnetic powder as a paint does not necessarily improve the media characteristics. It is hard to say that it is good.

Specifically, it has a 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 a magnetic recording layer with a coercive force (Hr) obtained from the residual magnetization curve of the magnetic recording medium and a coercive force (Hr) near H=Hr. d Hr / calculated from the half width (dHr) of the differential curve of the residual magnetization curve
Hr value is 0.5 or less, and the squareness ratio in the same direction as the head running direction in the saturation magnetization curve of the magnetic recording medium and the magnetic head in the running direction is 0.7 or more. It is something that

Operation The present invention has the above-described configuration, and is capable of achieving good output and C/N in the submicron region, and a C/N that cannot be achieved with the current combination of a coating type medium and a ring hend. 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 volumetric filling rate of the magnetic powder can be increased compared to conventional coated media, and the effective 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 prepare a magnetic paint.

・Plate magnetic powder (barium ferrite with an orthogonal crystal structure containing Co-Nb-Zn as a substituent element) (plate diameter 500 mm, plate thickness 150 mm, coercive force 9800e, saturation magnetization 63 emu/g) ・...200 parts Vinyl chloride polymer ...15
Part/Polyurethane...15
Part/Carbon...
Part 4: Alumina...
Part 8: Lubricant...
・2 parts・Solvent toluene ・・・・・・1
80 copies MEK・・・・・・180 copies・
Curing agent: 12 parts After filtering the obtained paint, the blade gap IOu
It was applied using an applicator of m.

A polyethylene terephthalate film with a thickness of 10 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 4500 Gauss. Next, calender treatment (90°C15
0 kg/d), and a curing treatment was performed at 60°C for 524 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 used as a magnetic powder whose surface was spinel-coated with barium ferrite, and paint preparation and tape production were carried out in the same manner as in Example 1.

The magnetic powder used for the paint had a plate diameter of 550 mm, a plate thickness of 180 mm, a coercive force of 9000 e, and a saturation magnetization of 68 emu/g.

Examples 3 and 4 In Examples 3 and 4, the magnetic powder used for making paint was
- Example 1.2 except that magnetoplumbite type barium ferrite magnetic powder having a substituent element of Ti-Zn and magnetoplumbite type barium ferrite magnetic powder having Sn-Mg as a monomer element were used. I made it into a tape according to the following.

Comparative Example 1 Comparative Example 1 followed Example 1 except that barium ferrite magnetic powder belonging to an orthogonal system in which the substitutional element was Co--Ti was used. Particle size is 800 mm, plate thickness is 130 mm, coercive force is 9
100e, and the saturation magnetization was 64e mu/g.

Comparative Example 2 In Comparative Example 2, a tape was formed in accordance with Example 2, except that a blended magnetic powder obtained by mixing barium ferrite with a magnetoplumbite structure and magnetite, which is a spinel ferrite, was used.

Comparative Example 3 and Comparative Example 4 In Comparative Examples 3 and 4, tapes were formed in the same manner as in Example 1.2 except that the orientation treatment was not performed.

Comparative example 5 Comparative Example 5 was a commercial MII-MP tape.

The sample obtained in this way was slit into 1/2 inch width, and the electromagnetic conversion characteristics were measured at a relative speed of 3.80 m/sec.
c. Measured using a metal laminated head (gap length 0.20 μm, track width 208 m, number of turns 25).

The recording frequencies used for measurement were 0.5, 1, 2, 3.5.5
．． It is 7.9MHz.

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.

(Margin below) The output shows the value at the optimum recording current, and is shown as a relative value based on the output of Comparative Example 5. is the longitudinal direction of the medium,
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 addition, in the examples, the plate-shaped magnetic powder was Co-NbZn
Although Ni-Ti-Zn and Sn-Mg substituted barium ferrite were used, the present invention is not limited thereto, and any material belonging to the hexagonal system may be used, and strontium ferrite or lead ferrite may also be used. Further, in Example 2, barium ferrite coated with excess spinel ferrite was used, but the present invention is not limited to this.

Effects of the Invention As described above, the magnetic recording medium of the present invention has the following characteristics: the coercive force (H') obtained from the residual magnetization curve in the running direction of the magnetic recording medium and the magnetic head, and the residual magnetization curve near H=Hr. d Hr / calculated from the half width (dHr) of the differential curve
Since the Hr value is 0.5 or less and the squareness ratio in the saturation magnetization curve measured in the running direction of the magnetic recording medium and magnetic head is 07 or more, the tape characteristics can be surpassed by commercially available metal tapes. can. 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) In a magnetic recording medium obtained by kneading plate-shaped magnetic powder and an additive/organic binder to prepare a magnetic coating material, and then applying the magnetic coating material onto a non-magnetic substrate, The value of dHr/Hr calculated from the coercive force (Hr) obtained from the residual magnetization curve and the half width (dHr) of the differential curve of the residual magnetization curve near H=Hr is 0.5 or less, and the magnetic recording medium and a magnetic recording medium having a squareness ratio of 0.7 or more in the same direction as the head running direction in the saturation magnetization curve in the running direction of the magnetic head. (2) The magnetic recording medium according to claim (1), wherein the plate-shaped magnetic powder has a crystal structure belonging to a hexagonal 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.