JPH01154319A - Production of digital magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve electromagnetic characteristics by subjecting a resin, fine ferromagnetic material powder and additive to a classification treatment by air flow. CONSTITUTION:The resin filler and magnetic powder which are raw materials are charged into a raw material feed port 1 and the high-pressure compressed air is rapidly ejected from a jet ejection part 2b to execute the jet process classification treatment, by which the resin and magnetic powder are classified. The uniform mixing and compactness of the resin, filler and magnetic powder of the recording medium are enhanced. Surface roughening is obviated and the higher electromagnetic effect is obtd. when kneading and dispersing with a kneader, kneading and dispersing with a ball mill, kneading and dispersing with a sand mill, etc., are effectively acted after the treatment.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention provides a magnetic recording medium, in particular, a magnetic recording medium that improves high output, high S/N ratio, and good override characteristics by densifying magnetic powder, and also provides a smooth and highly stable coating. The present invention relates to a method for manufacturing high-quality magnetic recording media such as magnetic disks and magnetic tapes that have a thin film surface.

[Conventional technology]

The conventional manufacturing method for coated magnetic disks consists of raw material resin,
Magnetic disks were manufactured using magnetic powder as is.

For this reason, various electromagnetic improvements have been made to increase the effectiveness of magnetic powder.

Among these, the resin, magnetic powder, dispersibility and orientation of the magnetic powder, drying method of the magnetic coating film (airflow method is common), curing method, etc. are used. Among them, the conventional method is to increase the content of magnetic powder in the resin, but the higher the content, the more various kinds of deterioration occurs.For example, S/N,
Noise generation due to porosity 9 This is a problem because it interferes with mechanical strength, etc. (for example, Japanese Patent Application Laid-open No. 47606/1983)
.

[Problem that the invention seeks to solve]

In the prior art, the density of resins, additives (fillers, etc.), and magnetic powders through classification processing was not studied.

The purpose of the present invention is to increase the effectiveness of denseness by jet (airflow) classification processing of resin, filler, and magnetic powder as much as possible from an electromagnetic point of view, and to achieve high density and high override (○/W).
The object of the present invention is to provide a magnetic recording medium with a high S/N ratio.

[Means for solving problems]

An outline of the method of the present invention is shown in FIG. 1 (vertical type).

The resin and magnetic powder are effectively classified by putting raw materials into the container and quickly blowing out highly compressed air to perform jet classification.

FIG. 2 shows an outline of horizontal jet classification processing. In the same manner as above, the raw materials are put into the container.

Resin, filler, and magnetic powder are effectively classified by quickly blowing out highly compressed air and performing jet classification.

By the above method, a magnetic recording medium in which the recording medium layer is a thin film of around 1 μm, has very small irregularities on the film surface over the entire surface, has excellent surface smoothness, and has excellent electrical and magnetic properties. can be obtained.

[Function] Generally, in order to improve the quality of the recording/reproducing medium, it is sufficient to increase the residual magnetic flux. One way to achieve this is to increase the thickness of the coating film. However, increasing the coating thickness deteriorates the high frequency characteristics. In order to improve high frequency characteristics, it is necessary to reduce the thickness of the coating film and also to increase the density of the magnetic powder. Conventionally, it has been difficult to realize magnetic tapes with excellent surface smoothness and effective density, magnetic disks for high density applications, etc., with a coating film thickness of around 1 μm. Furthermore, with the increase in density and high coercive force (high Ha), override (0
/W) The issue of improving characteristics was also added.

The present invention overcomes the above-mentioned drawbacks. That is,
In particular, by classifying the raw material resin filler and magnetic powder using the jet method, the resin and filler of the recording medium,
Improve the uniform mixing and density of magnetic powder, and after treatment, kneader kneading and dispersion, ball mill kneading and dispersion, sand mill kneading and
By effectively working through dispersion, etc., there is no surface unevenness.
It can increase the electromagnetic effect.

Conventionally, for example, when a magnetic thin film of around 1 μm was formed on the surface of an aluminum disk using a centrifugal coating method, in order to compensate for the decrease in output due to the small film thickness, it was necessary to increase the orientation of the magnetic field and the magnetic powder content. It is being done. However, the conventionally adopted magnetic field orientation simply aligns the magnetic material in the recording and reproducing direction (B
The aim is to achieve a value of 0.70 to 0.08) at r78m.

In addition, increasing the magnetic powder content causes a decrease in resolution and mechanical strength, so there is a limit to this.
I keep it around 0%.

In recent years, as recording densities have increased, coating film thickness has become thinner, and as a result, lower electrical signal output and insufficient resolution at high frequencies have become more problematic. Therefore, in order to obtain a magnetic recording medium with high output and excellent resolution, a higher degree of electromagnetic effectiveness of magnetic powder has become necessary.

For example, when obtaining a magnetic disk with a recording density of 15,0 OOB P I or higher, the inner circumference of the disk is approximately 0.85±0.2 μm and the outer circumference is approximately 1.2±0.2 μm using the spin coating method.
A magnetic coating film having a thickness of 100 µm is formed, and after curing by heating, the magnetic coating film is ground to a thickness of about 0.45 μm or less at the inner circumference and about 0.75 μm or less at the outer circumference.

At this time, by finding high processing conditions, it becomes possible to obtain a high-density recording medium with excellent resolution at high frequencies.

The present invention has solved these problems in thin coating, and has no uneven coating thickness over the entire recording surface, excellent surface smoothness, and excellent electrical and magnetic properties. This made it possible to obtain magnetic recording media.

That is, the present inventors applied a magnetic paint, in which fine ferromagnetic powder (dispersed by a jet method) was dispersed in a polymer binder solution, on an aluminum disk using a spin coating method.
It has been found that by subjecting the undried magnetic disk to a magnetic field orientation treatment, it is possible to obtain a magnetic disk that is free from cracks, has a surface smoothness far superior to conventional ones, and has excellent electrical properties.

Hereinafter, the achievements and effects of the present invention will be explained in more detail based on the drawings and specific examples.

FIG. 1 (vertical classification) shows the concept of jet classification of raw materials using highly compressed air used in the present invention.

As shown in the figure, raw material inlet 1. Jet spouting parts 2a, 2b
is provided, and the outlet 3 for taking out the raw material after the classification process is controlled by a support 4. Note that the jet is ejected using highly compressed air.

The feature of the present invention is to effectively densify raw materials (resin, magnetic powder, filler, etc.) by jet classification treatment.

FIG. 2 (horizontal classification) shows the concept of another jet classification process used in the present invention. In FIG. 6, 11 is the raw material inlet, 20a, 20b.

20c, 20d, 20e, 20f, and 20g indicate the state of the ejection portion of each jet. Furthermore, in FIG. 2, the opening/closing opening 30 which is sorted and taken out from the spiral shape is shown in the support 4.
It is attached to 0.

A feature of the present invention is the dispersion and classification of resins, fillers, magnetic powders, etc., for densification and densification by combined use of jet classification treatment of raw materials.

〔Example〕

The present invention will be described in detail below based on Examples.

Example 1 Acicular Co-Epi-γ-FezOa (average particle size 0-32
0XO-045/'my coercive force 6300 e) 700
Heavy duty m2 polyvinyl butyral (PVB) 60 parts by weight (
powder) was simultaneously jet-treated (jet-o-mizer; vertical type) with 7 kg/aJ of compressed air.

60 parts by weight of single-crystal alumina powder was further added as an auxiliary agent to the powder classified by several micrometers, and kneaded with 600 parts by weight of 2-ethoxyethyl acetate (cellosolve acetate) for 4 hours.

780 parts by weight of the above mixed wire and 390 parts by weight of the solvent were placed in a ball mill pot and kneaded in a ball mill for 5 days to disperse the ferromagnetic powder. Next, 105 parts by weight of phenolic resin,
105 parts by weight of epoxy resin.

A magnetic paint for a magnetic disk was prepared by adding 900 parts by weight of a solvent.

Next, the above coating material was centrifugally coated at 1000 rPI11 onto an 8.8 inch aluminum substrate whose surface had been previously cleaned, and magnetic field orientation was performed using a well-known method. After the coated magnetic disk was cured at 200° C., the coating film thickness was measured. The film thickness of the obtained coated disk was around the inner circumference (R63
nn) with O-21p m at the middle circumference (R83mm) with 0.
45 μm, and the outer circumference (R103Ia) was 0.53.

For comparison, the inner circumference was 0.43 μm in the conventional process (without jet treatment).

It was 0.66 μm at the middle circumference and 0.73 μm at the outer circumference.

The coating thickness of this example, which was subjected to classification treatment, is based on the fluidity of the paint.

Excellent in high dispersion and high density, and along with this, S
An improvement of approximately 22% was observed in the /N ratio.

Example 2 Magnetic powder Co-Epi-γ-FezOs similar to Example 1
700 parts by weight, 60 parts by weight (made into several meters with epoxy resin) and 7 kg/a of each compressed air.
(Jet processing (single track jet mill; horizontal type).

Further, 60 parts by weight of single-crystal alumina powder was added as a reinforcing agent to each of the powders (classified into particles of several micrometers), and kneaded with 600 parts by weight of Serotul acetate in a kneader for 4 hours.

780 parts by weight of the above mixture and 390 parts by weight of the same solvent were placed in a ball mill pot, and kneaded in a ball mill for 5 days to disperse the ferromagnetic powder. Next, 105 parts by weight of phenol resin and 60 parts by weight of vinyl resin.

A magnetic paint for a magnetic disk was prepared by adding 75 parts by weight of epoxy resin and 900 parts by weight of the same solvent.

Next, the above paint was centrifugally applied at 100° rpm onto an 8.8 inch aluminum substrate whose surface had been previously cleaned, and magnetic field orientation was performed using a well-known method. After the coated magnetic disk was cured at 200° C., the coating film thickness was measured.

The film thickness of the obtained coating disc was 0 at the inner circumference (R63 mm).
．． 30 p m, 0.55 μm at the middle circumference (R83 mm).

The outer circumference (R103+m) was 0.64 μm.

For comparison, the conventional method (without jet treatment)
In the process of 0.52μm on the inner circumference and 0.68μm on the middle circumference
m, and the outer circumference was 0.79 μm.

Further, in the disk according to this embodiment, the electrical characteristics are S/
An improvement of about 17% was seen in the N ratio.

As described above, it can be seen that according to the method of the present invention, magnetic fine particles are effectively classified. Also,
Figure 1 shows resin, magnetic powder, and filler.

The results were almost the same as in Example 1 or 2 even when the classification process was carried out simultaneously or separately using the apparatus shown in FIG.

〔Effect of the invention〕

As explained above, the magnetic paint of the present invention has ferromagnetic powder uniformly dispersed in the paint and has good flow characteristics.
It can be 2000P, and the conventional method is 250cp ~
We succeeded in lowering the viscosity by about 10ocp compared to 300cp. The conventional method for lowering the viscosity mainly involved dilution with a solvent, which caused problems with dispersion, agglomeration, sedimentation, etc. However, the present invention does not cause such problems. Furthermore, the method of the present invention also improved the stability of the magnetic coating material against sedimentation by more than double.

[Brief explanation of the drawing]

FIG. 1 is a schematic vertical sectional view of a jet stream classification device suitable for carrying out the present invention, and FIG. 2 is a cross sectional view of another type of classification device. 1.11--Raw material inlet, 2a, 2b, 20a, 20b
.

Claims (1)

[Claims] 1. Manufacturing a digital magnetic recording medium in which a magnetic recording layer is provided by dispersing ferromagnetic fine powder and various additives in a polymeric binder, coating it on a non-magnetic support, orienting it, and thermosetting it. 1. A method for producing a digital magnetic recording medium, characterized in that the resin, fine ferromagnetic powder, and additives are classified by air flow.