JPS6216245A - Production of magnetic recording medium - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Summary] This specification discloses a magnetic recording medium having a coating film of a magnetic paint containing magnetic powder, and a method for manufacturing such a magnetic recording medium. The magnetic recording medium of the present invention has particularly low noise and excellent mechanical strength. The magnetic recording medium of the present invention also has excellent magnetic properties.

[Conventional technology]

In order to manufacture magnetic recording media such as magnetic tapes and magnetic disks, Ba ferrite (Babe, etc.) is used, for example.

OI, ), γ-ferrite (γ-FezO3) + spherical C
It is well known that a desired recording medium is obtained by coating a magnetic paint containing magnetic powder such as O on a sheet-like or disk-like base (support). The magnetic coating film on the base is usually dried while being oriented in a strong magnetic field to form a perpendicular recording medium. Manufacture of magnetic recording media using this coating technology includes the Subafuta method,
It is easier to carry out than manufacturing by vacuum evaporation, plating, etc., and the magnetic properties of the resulting recording medium are also very good.

Magnetic paints used in the manufacture of such magnetic recording media are generally prepared by kneading selected magnetic powders with magnetic paint-forming components such as binder resin, thinner (solvent), and reinforcing agents.

The reinforcing agent is mixed into the magnetic paint to increase the mechanical strength of the resulting recording medium, and alumina powder is widely used. For kneading, a ball mill, sand grinder, etc. can be used.

[Problem that the invention seeks to solve]

In manufacturing magnetic recording media using the coating technology described above,
When a reinforcing agent is used to improve mechanical strength, there is an undesirable problem in that magnetic noise increases. In order to solve this problem of magnetic noise, attempts have been made to improve the dispersibility of the reinforcing agent in the magnetic paint (), but satisfactory results have not been obtained. For example, when a ball mill is used to mix and purify a paint, it takes a long time to knead due to the low dispersion ability of this means, and the dispersibility of the reinforcing agent in the resulting paint cannot be improved by using other means, such as Not as good as using a sand grinder. Although attempts have been made to carry out ball milling using hard poles such as zirconia, the dispersibility of the reinforcing agent cannot be significantly improved. On the other hand, when kneading is carried out using a sand grinder, breakage of the magnetic powder becomes noticeable due to the excessively high dispersion ability of this means, and therefore the magnetic properties tend to deteriorate.

The above are the problems that the present invention attempts to solve. In other words, an object of the present invention is to provide a magnetic recording medium with low noise and excellent mechanical strength and magnetic properties, and a method for manufacturing the same.

[Means for solving problems]

According to the present invention, the above-mentioned problems can be solved by magnetic recording having a coating film of magnetic paint containing magnetic powder, binder resin, thinner, reinforcing agent, etc. (hereinafter, these components are referred to as "magnetic paint forming components"). In producing the medium, first, a reinforcing agent liquid is prepared in advance by kneading a reinforcing agent with poor dispersibility in a magnetic paint with a magnetic paint forming component that does not contain magnetic powder using a kneading means with high dispersion ability. The problem can then be solved by kneading this reinforcing agent liquid with magnetic powder or a magnetic paint containing magnetic powder using a conventional kneading means. 1st and 2nd above
The magnetic paint obtained as a result of the adulteration of
It can be applied onto a suitable base using conventional application means.

In the practice of the present invention, reinforcing agents such as alumina powder, SiC powder, etc. are combined with a binder resin such as acrylic resin and the like and toluene.

Advantageously, the reinforcing agent solution is prepared by kneading in a sand grinder with a thinner such as cellosolve acetate, benzyl alcohol, etc. A ball mill can advantageously be used to knead the resulting reinforcing agent liquid with the magnetic paint.

Magnetic powders advantageously used in the practice of the present invention include:
As mentioned above, BaFetzO+q l T Fez
O:+.

Spherical Co, etc.

A magnetic paint containing magnetic powder can be applied onto the base using an application technique such as spin cording. The base used here can have the shape of a sheet, a disk, etc. and can consist of a plastic material, such as polyester, polyethylene terephthalate, or a metallic material, such as aluminum.

〔Example〕

The following ingredients: Alumina powder (reinforcing agent) 80 parts by weight Acrylic resin (binder) 30 parts by weight Thinner: Toluene 180 parts by weight Cellosolve acetate 70 parts by weight Benzyl alcohol x
A reinforcing agent was prepared by carefully kneading the out part in the stated amount in a sand grinder for 6 hours.

The reinforcing agent was uniformly dispersed in the obtained reinforcing agent liquid.

The predispersed reinforcing agent solution prepared as described above was mixed in the following magnetic coating composition in the following amount and kneaded in a plastic ball mill for 5 days.

Magnetic powder (r -FezO+) 55 parts by weight Reinforcement liquid 7 parts by weight Epoxy resin 22.5 parts by weight Acrylic resin
13.5 parts by weight phenolic resin 9.
0 parts by weight Toluene 150 parts by weight Xylene 150 parts by weight Cellosolve acetate
50 parts by weight benzyl alcohol
After kneading 50 fEt parts, the state of the obtained magnetic paint was observed, and it was found that the reinforcing agent was still uniformly dispersed in the paint, and the needle crystals of the magnetic powder were not destroyed.

11. Apply the approved magnetic paint to an aluminum substrate with a film thickness of approximately 1 μm.
It was coated with The coating technique used for this coating was a spin code method. The obtained recording medium with the coating film was dried while being oriented in a strong magnetic field, and then a magnetic disk was completed by the following conventional means. The magnetic noise of the medium, the degree of orientation of the magnetic powder, and the mechanical strength of the medium (by C5S test) were evaluated. The results shown in Table 1 below were obtained.

In order to compare soil and soil, the method described in Example 1 was repeated with different conditions such as the reinforcing agent solution.

Comparative Example 1: No reinforcing agent liquid was used in the preparation of the magnetic paint, and instead, the same amount (7 parts by weight) of alumina powder was used.

Comparative Example 2: No acrylic resin was used in preparing the reinforcing agent liquid, and instead, the same amount (30 parts by weight) of epoxy resin was used.

Comparative Example 3: No acrylic resin was used in preparing the reinforcing agent liquid, and instead, the same amount (30 parts by weight) of phenolic resin was used.

Comparative Example 4: No plastic ball mill was used to prepare the magnetic paint,
Instead, I used a sand grinder. The kneading time was 6 hours.

The results shown in Table 1 below were obtained.

Table 1 in the margin below - Example 1 8 0.81 Comparable example 1
15 0.78 Comparable example 2 1
3 0.79 Comparable example 3 14
0.78 Comparable example 4 13
0.75 Fair * Mechanical strength was evaluated as "fair" when the medium was subjected to a CSS test and the result was 100,000 times or more.

From the above results, it can be seen that according to the present invention, it is possible to reduce medium noise without impairing magnetic properties and to obtain a recording medium having excellent mechanical strength. Furthermore, it can be seen that special effects can be exhibited by using acrylic resin as the binder resin used in carrying out the present invention. In addition, reinforcing agent liquid and magnetic paint (contains magnetic powder)
It is also found that the use of a sand grinder must be avoided for kneading.

To confirm that acceptable mechanical strength could not be obtained in the absence of the tensile reinforcing agent, the procedure described in Comparative Example 1 was repeated without also using alumina powder. Part ■ below
Unacceptable results were obtained as indicated in the table.

Furthermore, in order to find out the relationship between the magnetic paint preparation conditions and the properties of the resulting medium, we have summarized some data from previous examples in the following Table 2.

■Table example 1 Ball reinforcement 20 8 0.81
As shown in the above results, the magnetic recording medium that does not use a reinforcing agent (Comparative Example 5) has low mechanical strength, but has low media noise, a high degree of orientation, and has the best magnetic properties. ing. When only a reinforcing agent is added to this recording medium (Comparative Example 1), the mechanical strength increases, but the medium noise increases and the degree of orientation deteriorates. This shows that addition of only the reinforcing agent results in poor paint dispersion. On the other hand, when a reinforcing agent liquid was used and a sand grinder was used to knead the paint (Comparative Example 4), even though the kneading time, that is, the relative paint preparation time in Table 1, was much shorter, It can be seen that the media noise is smaller and the dispersibility is improved compared to the case of using the agent alone or using a ball mill. However, in this case, although the dispersibility is good, the degree of orientation is poor, and the magnetic powder may even break due to the strong kneading ability of the sand grinder. In Example 1, which is an example of the present invention, although the kneading time is longer, the above-mentioned disadvantages do not exist.

〔Effect of the invention〕

In the present invention, since the reinforcing agent liquid is prepared using a kneading means with high dispersion ability, it is possible to achieve satisfactory and sufficient dispersion of the reinforcing agent in this liquid.
The magnetic noise of the resulting medium can be kept low. Further, according to the present invention, since the reinforcing agent and the magnetic powder are not kneaded in direct contact with each other, it is possible to avoid deterioration of the magnetic properties due to breakage of the magnetic powder or the like. Furthermore, according to the present invention, since a reinforcing agent is used, excellent mechanical strength can be obtained.

Claims (1)

[Claims] 1. A method for manufacturing a magnetic recording medium having a coating film of a magnetic paint containing magnetic powder, which comprises mixing a reinforcing agent with a magnetic paint forming component other than the magnetic powder to obtain a reinforcing agent liquid. Then, this reinforcing agent liquid is kneaded with magnetic powder alone or with a mixture of magnetic powder and other magnetic paint forming components to obtain a magnetic paint, and this magnetic paint is subsequently applied onto the base. Manufacturing method for magnetic recording media. 2. The manufacturing method according to claim 1, wherein a reinforcing agent liquid is prepared by kneading the reinforcing agent with a binder resin and a thinner. 3. The manufacturing method according to claim 2, wherein kneading for preparing the reinforcing agent liquid is performed using a sand grinder. 4. The manufacturing method according to claim 2, wherein the binder resin is an acrylic resin.