JPS6265238A - Production of magnetic recording medium - Google Patents

Abstract

PURPOSE:To eliminate a stage for an orientation treatment and to maintain the residual magnetization/saturation magnetization ratio of a magnetization curve at a prescribed value by preparing a magnetic coating compd. for which hexagonal magnetic material powder of a prescribed grain size having uniaxial anisotropy is used and coating such coating compd. on a substrate, then drying the coating. CONSTITUTION:The magnetic coating compd. is prepd. by using the hexagonal magnetic material powder having the uniaxial anisotropy and 0.01-0.3mum grain size. The magnetic coating compd. prepd. in such a manner is coated on the substrate and is dried, by which the stage for an orientation treatment is elimi nated and the manpower, electric power, etc., are lessened. Hexagonal ferrite or the substituent thereof is used for the hexagonal magnetic material. The ratio of the residual magnetization/saturation magnetization of the magnetization curve formed by subjecting the magnetization curve adjusted in the direction perpendicular to the medium surface to a diamagnetic field correction is set at 0.3-0.7.

Description

Detailed Description of the Invention [Objective of the Invention] (Field of Application in the JLC Industry) The present invention relates to a method for manufacturing a magnetic recording medium, and particularly to a method for producing a magnetic recording medium based on a non-oriented hexagonal-axis anisotropic magnetic powder. The present invention relates to a method for manufacturing a medium suitable for high-density magnetic recording, which is coated on a material.

(Prior art) Conventionally, for magnetic recording and reproduction, magnetic powder made of acicular crystals such as γ-Fe2O3°CrO2 is oriented in the in-plane longitudinal direction of the recording medium, and residual magnetization in the in-plane longitudinal direction is utilized. The most common method is to However, this recording and reproducing system has the disadvantage that the demagnetizing field within the magnetic recording medium increases as the recording density increases, and recording regeneration is particularly poor in the short wavelength region. In order to overcome this demagnetizing field and perform high-density recording, it is necessary to increase the coercive force of the recording medium and thin the magnetic recording layer. However, currently it is difficult to increase the coercive force of the magnetic recording layer, and Making it thinner has problems such as degrading the characteristics of the reproduced signal. After all, it is difficult to achieve high density magnetic recording using the conventional method of orienting acicular r magnetic powder in the in-plane longitudinal direction and utilizing residual magnetization in this direction.

Therefore, a method using residual magnetization in the direction perpendicular to the surface of the magnetic recording medium was proposed. In such a perpendicular magnetic recording system, it is necessary to have an axis of easy magnetization in a direction perpendicular to the recording medium surface, and the following recording media have been proposed.

One is one in which a Co--Cr alloy film is formed on the surface of a base material by sputtering. However, this recording medium has C.
By sliding the o-Cr alloy film and the magnetic head, recording V
It is difficult to put it into practical use because of its drawbacks, such as excessive wear and tear on both the magnetic head and the recording medium itself, which is difficult to handle due to its poor flexibility, and low manufacturing productivity. Met.

In addition, as a coated perpendicular magnetic recording medium in which a magnetic recording layer is formed by applying magnetic powder to a base material together with an organic binder, B containing Fe3O4 polyhedrons and substitutional elements as a magnetic material is used.
It has been proposed that a powder such as a-ferrite is used and the powder is oriented in a direction perpendicular to the surface of the recording medium. In this type of recording medium, recording and reproduction in the short wavelength region are improved, and the density of one recording is also +j (capacity). , compared to a conventional recording medium in which acicular magnetic material is oriented in the in-plane length direction, the 11 raw output is unstable.Also, with this recording medium, the conventional ring-shaped magnetic head has the disadvantage that the l+ !There is also the disadvantage that there are no 11 records.

From the viewpoint of manufacturing technology, all conventional coated/Ii type media have been subjected to magnetic field orientation treatment, regardless of the method that utilizes the residual magnetization in the 0-plane direction, or the method that utilizes the residual magnetization in the vertical) j direction. Regardless of the method used, a magnetic field orientation process that orients the easy axis of magnetization of the ia magnetic material in that direction is essential.However,
Such magnetic field alignment processing requires special equipment and power, such as alignment magnets and mechanical alignment equipment, so if this step can be eliminated, the first step in production can be done in the cylinder, which would save labor. Benefits: 5.
It was also true that there was an IG.

So far, we have developed 11 trees containing acicular magnetic materials.
There is an example of a magnetic recording medium in which a paint is applied to the surface of a substrate and allowed to dry without being subjected to magnetic field alignment treatment. Even in this case, increasing the recording density depends on the utilization of the residual magnetization of the magnetic material oriented in a direction perpendicular to the surface of the recording medium, but in reality, increasing the recording density depends on It was not something that could be achieved. This is because the residual magnetization component in the vertical direction is very small. Because of this process, the la magnetic field orientation treatment has been considered an essential step.

As explained in detail below, it is almost impossible to increase the recording density with some acicular magnetic materials.On the other hand, it is possible to increase the recording density with Fe3O4 polyhedrons and substituted Ba ferrites, but it is difficult to use as a recording medium. Various difficulties and problems still exist, and it is not satisfactory for practical use. Furthermore, given the past history, magnetic field alignment treatment is considered to be indispensable for coated recording media, and pursuing the advantages of SJ fabrication by omitting this process is a side issue. It wasn't a discussion that should have taken place.

(Problem to be solved by the invention [Qi]) Based on the above-mentioned technical level, the present invention solves the problems listed in F that the conventional high-density magnetic recording media had, and moreover, it does not require magnetic field orientation treatment T. An object of the present invention is to provide a H'i method for manufacturing a high-density magnetic recording medium that can be manufactured in a number of steps.

[Structure of the Invention] (Means for Solving the Problems) To briefly describe the present invention, particles PIO, Ol = 0, 3 g of magnetic powder consisting of hexagonal and uniaxially anisotropic crystals are prepared. The ratio of residual magnetization/saturation magnetization of the magnetization curve obtained by demagnetizing field correction of the magnetization curve determined perpendicular to the medium surface by coating and drying the containing resin Mll on the metal forming base material (hereinafter referred to as r-square ratio) ) between 0.3 and 0.7
This is a method of manufacturing a magnetic recording medium in which the cost is 4 yen.

In a magnetic recording medium, if each particle of the m-type substance is completely oriented in different directions and exists in a so-called non-oriented state, the squareness ratio will be 0.5, but as in the present invention, the squareness ratio is 0.3. ~0.
If the squareness ratio is in the range of 7, it is 1-minute.If the squareness ratio is less than 0.3, there will be fewer vertically oriented particles with respect to the recording medium, and there will be fewer vertically oriented particles. #I If the squareness ratio exceeds 0.7, there will be too many vertically oriented particles, which will lead to problems with conventional perpendicular magnetic recording media, such as unevenness on the surface of the magnetic recording layer and decreased output. Things like destabilization.

This is undesirable because it causes problems such as being unsuitable for conventional ring-shaped heads.However, what is most noteworthy here is that the high-density recording characteristics produced by the present invention do not require any magnetic field alignment treatment. It is possible to manufacture
This is because the basolateral prediction cannot be obtained from the above-mentioned results when 31-shaped particles are used as the magnetic material.

Specific examples of the magnetic material composed of hexagonal and uniaxially anisotropic crystals used in the present invention include Ba and Sr.

Hexagonal ferrites such as Pb and Ca'9 ferrites and a part of the Fe of the ferrites are replaced with Co and Ti.

Zn, Nb, Ta, Sb, etc. substituted with Te, or an alloy Co-Ni whose main component is CO.

Co-Fe is an example, but substituted hexagonal ferrite is particularly frightening.These magnetic powders have a particle size of 0.01
It needs to be in the range of ~0.3μ. If it is less than 0.01, it will no longer exhibit ferromagnetism and cannot be used for magnetic recording.
Moreover, if it exceeds 0.3-, it becomes unsuitable for high-density recording.

(The order in which the resin composition containing magnetic powder is applied to the material may be according to the conventional method.)
Acid-resistant vinyl conjugate, urethane! ! Magnetic powder is dispersed in a composition consisting of a resin such as lubricant or cellulose derivative, an anionic, nonionic, or cationic dispersant, a curing agent, and an appropriate effective solvent if necessary. Just apply it to the base material using a doctor blade etc.
Thereafter, a magnetic recording medium is obtained by drying.

The magnetic recording medium of the present invention is a medium suitable for high-density recording, which can perform stable recording and reproduction, and can also use ring-shaped magnetism, which is currently the mainstream. Moreover, since it can be manufactured without magnetic field alignment treatment, it is a recording medium that is advantageous in terms of labor saving, power saving, and low cost.

Examples will be specifically described below.

Example A solution containing chlorides of Ba and Fe and additives for reducing coercive force, ie, chlorides of Co and Ti, and NaOH, Na2
After mixing with an alkaline solution using CO3 to obtain a precipitate, this was washed and the dried powder was calcined at 900°C for 2 hours to obtain a plate-shaped Co - Ti m exchanged Ba ferrite powder. . As a result of microscopic observation, the particle size of this powder was 0.05-
This powder was mixed with a dispersant such as lecithin and a resin such as urethane or vinyl chloride.
The coating material 1 obtained by combining and dispersing the coating material was applied to a polyethylene terephthalate base material to a thickness of about 3 mm using a doctor blade, and after drying, the surface was smoothed by calendering. The magnetization curve obtained by demagnetizing field correction of the magnetization curve of the recording medium thus obtained is shown in FIG. 1. From this figure, the squareness ratio was 0.48. Figure 2 shows the recording density and reproduction output of this recording medium when recording is performed using the currently used ring-shaped head (curve A). , 15g, track width 35-, the currently used in-plane longitudinal direction acicular particles (Co-coated γ-Fe203
) is also shown at the same time as the value of the recording medium oriented (curve B)
However, it can be seen that the magnetic recording medium obtained according to the present invention exhibits excellent high-density recording characteristics.

Comparative Example The magnetic paint used in the above example was applied onto a substrate in the same manner as in the example, and before the paint dried, a magnetic field of 4 KOe was applied in the direction perpendicular to the medium to perform orientation treatment. , and then dried and calendered to produce a magnetic recording medium. The squareness ratio of this magnetic recording medium was 0.80. Further, the surface roughness was 0.06-, which was larger than the surface roughness of the recording medium of Example, which was 0.02-. Further, the reproduction output measured in the same manner as in the example was 12 dB compared to the reproduction output of the example, and the output-to-noise ratio was similarly low at 13 dB.

[Brief explanation of drawings]

FIG. 1 shows a magnetization curve obtained by demagnetizing field correction of the magnetization curve measured in the direction perpendicular to the medium surface of the magnetic recording medium of the present invention;
FIG. 2 shows the relationship between the recording density and reproduction output of the recording medium A and the comparative recording medium B. 0.1 0.30.5 1.0 3.0
'K'Iti-'J &(10'/cm>Fig. 2

Claims (2)

[Claims] (1) A magnetic paint is prepared using a uniaxially anisotropic hexagonal magnetic powder having a particle size of 0.01 to 0.3 μm, and then the magnetic paint is substantially oriented on a substrate. By coating and drying without applying any A method for manufacturing a magnetic recording medium. (2) The manufacturing method according to claim 1, wherein the hexagonal magnetic material is hexagonal ferrite or a substitute thereof.