JPS60211635A - Production of magnetic recording medium - Google Patents

Abstract

PURPOSE:To produce a magnetic paint which obviates intrusion of medium powder and to obtain an excellent magnetic recording medium by using balls consisting of SiC or Si3N4, etc. as a medium for a high-speed medium stirring type mill to mix and disperse a paint contg. magnetic metallic powder and nonmagnetic powder having specific hardness or above. CONSTITUTION:The balls, beads, etc. consisting of SiC or Si3N4 and having about 1.3mm. average grain size are used so as to be thoroughly dispersed in the paint in the high-speed stirring type mill in a way as to obviate generation of the abrasive powder of the magnetic metallic powder by the nonmagnetic powder such as alumina, chromium oxide or the like having >=6 Mohs' hardness without cracking of the balls which are the medium in the stage of mixing and dispersing the magnetic paint contg. said magnetic powder and nonmagnetic powder and preparing the magnetic paint by using said mill. The magnetic paint without contg. the worn powder and splinters of the medium in the mill is thus obtd. and the magnetic recording medium having excellent electromagnetic transducing characteristics, etc. is manufactured.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a magnetic tape having a metal magnetic layer comprising a metal magnetic layer) and a non-magnetic layer having a Mohs hardness of 6 or more.

The present invention relates to a method of manufacturing magnetic recording media such as magnetic disks.

[Background technology]

A magnetic recording medium formed by coating a base with a magnetic paint containing metal magnetic powder has the disadvantage that the magnetic layer is prone to wear and tear because the magnetic powder has low hardness and is soft. Therefore, in order to avoid this drawback, a magnetic recording medium is created in which a relatively large amount of non-magnetic powder with a Mohs hardness of 6 or more is added and mixed into a magnetic paint, and this is coated on a base.
Are known.

However, when preparing this type of paint using a high-speed media stirring type mill, the glass piece that is the media has a Mohs hardness of 6.
These non-magnetic powders are easily abraded, and this not only causes problems such as clogging of screens or gaps when replacing beads or separating beads after paint preparation, but also causes problems such as clogging of screens or gaps when beads are replaced and beads are separated after paint preparation. The problem has been that the surface smoothness of the magnetic layer formed using the paint and the packing density of the magnetic powder are reduced, and the electromagnetic conversion characteristics are greatly impaired.

The above-mentioned high-speed media stirring type mill is generally praised for its ability to mix and disperse high-viscosity paint formulations continuously and efficiently, but due to its mill structure, it is applied to ball mills. High specific gravity media such as steel balls cannot be used. For this reason, in the past, glass beads with a relatively low specific gravity and low cost have been used, but these beads have poor abrasion resistance and therefore do not suffer from the drawbacks mentioned above for certain paint formulations. There wasn't.

Therefore, in place of the conventional glass beads, it is desirable to use a medium similar to the glass beads, which has a light specific gravity, high hardness, and is resistant to wear. Furthermore, it is desirable that even if this medium were to wear out to a small extent and get mixed into the magnetic head 1', it would not have much of an adverse effect on the electromagnetic conversion characteristics of the magnetic recording medium.

By the way, in addition to the steel balls mentioned above, alumina (aluminum oxide) balls and zirconia (zirconium oxide) balls are known as balls used in ball mills, and these balls have relatively light specific gravity and high hardness. .

In addition, many of the non-magnetic powders with a Mohs hardness of 6 or higher contained in magnetic paints are composed of oxides such as alumina, chromium oxide, titanium oxide, and iron oxide, and each of the above balls is made of these non-magnetic powders. Since it is made of the same type of oxide as the powder, it is believed that the abrasion powder has little effect on the electromagnetic conversion characteristics.

After this idea, attempts were made to use the above-mentioned alumina balls and zirconia balls as a medium for a high-speed medium single-stirring mill. However, since alumina balls are inherently fragile as ceramic sintered bodies,
If a paint formulation contains the above-mentioned high-hardness non-magnetic powder, cracks and fractures are likely to occur due to contact with this non-magnetic powder, and in this case, much larger abrasion powder is produced than with non-magnetic powder. This abrasion powder is mixed into the magnetic paint, and when a magnetic head is brought into contact with a magnetic tape made using this paint, the spatula I~ is worn out.

On the other hand, zirconia balls have a slightly higher specific gravity than glass beads or alumina balls ((specific gravity 5.5-6°3), so they have poor dispersion efficiency as a medium for high-speed media stirring type mills, which is why they have poor dispersibility. The problem was that it was difficult to obtain magnetic paint, and therefore no significant improvement in electromagnetic conversion characteristics could be expected.

In addition, although it can be said that the amount of wear of alumina balls and zirconia balls themselves during paint preparation is less than that of glass beads, it still accounts for a considerable amount of wear.
As a result of this being mixed into the magnetic paint, even though this mixed material is composed of the same type of oxide as the non-magnetic powder as a paint component, it still has a negative effect on the electromagnetic conversion characteristics as a magnetic recording medium. I couldn't.

[Purpose of the invention]

From this point of view, the present invention uses oxidized alumina balls, zirconia balls, etc., which have a light specific gravity, high hardness, do not easily generate large RF abrasion, and have a small amount of wear as a medium for a high-speed media stirring type mill. By exploring media different from physical media, the objective is to obtain a magnetic recording medium with excellent electromagnetic conversion characteristics and less head wear.

[Summary of the invention]

In order to achieve the above object, the inventors conducted extensive studies and found that when using silicon carbide or silicon nitride, which had not been previously used as a medium in a high-speed media stirring type mill, the electromagnetic conversion characteristics The inventors realized that it is possible to obtain a magnetic recording medium that is superior in quality and exhibits less wear on the head, leading to the completion of this invention.

That is, this invention produces a magnetic paint by mixing and dispersing a paint composition containing a metal magnetic powder and a non-magnetic powder with a Mohs hardness of 6 or higher using a high-speed media stirring type mill, and then coats this paint on a base. The present invention relates to a method of manufacturing a magnetic recording medium, characterized in that silicon carbide or silicon nitride is used as the medium of the high-speed medium stirring type mill.

In this invention, silicon carbide and silicon nitride used as the medium of the high-speed media stirring type mill are SiC and S 1 z
It is a silicon carbide or nitride represented by a molecular formula such as Np, and all of these compounds have a light specific gravity of about 3.2 and a high hardness of Mohs hardness of 12 or more.

Furthermore, unlike alumina, it does not have the properties of a ceramic sintered body, so it has the advantage of being less likely to generate large abrasion powder due to cracks and cracks, and also has the characteristic that the amount of wear is small.

1. Rhinocarbide and silicon nitride are used in the form of balls, beads, and pebbles depending on the structure of the mill. The size varies considerably depending on the above-mentioned form, but generally the average particle size is 0.5 to 3 mm, preferably 1 to 7 mm.
．． It is appropriately set within the range of mm.

This high-speed media stirring type mill that uses silicon carbide and silicon nitride as media violently stirs the media. L-
14 It can be widely used as long as the contents can be mixed and dispersed by shearing and friction. Examples of means for stirring the medium include a disc-shaped disk, a rod-shaped pin, and a plate-shaped arm. Alternatively, it may be an annular type mill in which a medium is inserted between an inner cylinder and an outer cylinder, and the contents are mixed and dispersed by applying a strong pneumatic action to the medium by rotating the inner cylinder. .

In this invention, a magnetic coating material is prepared by loading at least one selected from silicon carbide and silicon nitride as a medium and a coating composition into the above-mentioned mill, and mixing and dispersing this composition. . The above compound contains a metal magnetic powder and a non-magnetic powder with a Mohs hardness of 6 or more, and also contains a binder, a solvent, or a dispersion medium as other essential components, and if necessary, a lubricant and an antistatic agent. , additives such as surfactants are added.

As the metal magnetic powder in the paint formulation, ferromagnetic metal powder or alloy powder such as iron or cobalt is used, and the alloy powder may partially contain a non-magnetic metal. The average particle diameter (long axis) of this metal magnetic powder is usually 0.15.
It is about 0.30 μm.

Further, as the non-magnetic powder having a Mohs hardness of 6 or more, oxide-based powders such as alumina powder, chromium oxide powder, Titania 45), and Hengara powder are preferable, but other non-magnetic powders may also be used. The particle size of these non-magnetic powders is as follows:
The average particle diameter (long axis) is about O12 to 1.0 μm.

The above 3 types of magnetic powder are generally made of gold, in order to prevent a decrease in the wear resistance of the magnetic layer, which is a drawback of metal magnetic powder.
The proportion used is 2 parts by weight or more and usually up to 10 parts by weight per 100 parts by weight of the 51-year-old fish. In this way, Jori's non-(d
Since one powder is required, the problem of abrasion of the milling medium arises. However, in the present invention, the above-mentioned problem is avoided by using silicon carbide and silicon nitride as the milling medium.

As the binder in the paint formulation, any conventionally known binder such as vinyl chloride-vinyl acetate copolymer, polyurethane, polyester, fiber cord resin, polyvinyl butyral, polyisocyanate, etc. can be used. Also, as a solvent or dispersion medium, use the binder described in 1. A soluble or dispersible organic solvent, water, etc. are used.

After preparing the magnetic paint in this way, by applying this paint on the base using a conventional method, magnetic tape,
It is possible to obtain a magnetic recording medium that has excellent wear resistance and electric 6d conversion characteristics such as magnetic disks, and has a small amount of wear on the head.

〔Effect of the invention〕

As is clear from the above description, in this invention, silicon carbide or nitride cable, which has a light specific gravity, high hardness, and is resistant to cracks and cracks, is used as the medium of the high-speed media stirring type mill. The dispersibility of the additive composition is improved, and the electromagnetic conversion property can be improved by 1υ1, and a magnetic recording medium with less head wear can be obtained.

In addition, - silicon carbide or silicon nitride have less wear compared to alumina or zirconia, so even though they are made of a non-oxide compound different from the non-magnetic powder in the paint component, the magnetic The recording medium has excellent electromagnetic conversion characteristics that take advantage of the good dispersibility of the coating composition.

Furthermore, since there is less wear on the mill media during the mixing and dispersion process of paint formulations, there is no need to replace the media, which was unavoidable with conventional glass beads, or to clog screens or gaps when separating the media after paint preparation. This problem is also avoided.

〔Example〕

EXAMPLES Below, examples of the present invention will be described in more detail. In the following, parts shall mean parts by weight.

Example 1 Metallic iron powder 100 parts Vinyl chloride-vinyl acetate 10 parts - Hinyl alcohol copolymer polyurethane 10 parts Polyisonoir - 1.5 parts Cyclohenite → Nano 7 120 parts Toluene 120 parts Carbon black 3 parts Alumina 1 minute 4 parts 1 part liquid paraffin 1 part lauric acid The above coating composition was mixed at a feed rate of 100 g using a high-speed media stirring type mill (Annular type) using silicon nitride pieces with an average particle size of 1.3 mm as the medium. A magnetic coating material was prepared by performing four passes under the following conditions: 10 m/min, an In stirring speed of 10 m/sec, and a temperature of 40''C.

The magnetic tape of the present invention was prepared by drying this paint on a 14 .mu.m thick polyester haze film so that the dry thickness became 4 .mu.m.

Example 2 Instead of nitrided +) group beads, average particle diameter 1.3 mm
A magnetic tape of the present invention was produced in exactly the same manner as in Example 1, except that silicon carbide beads were used.

Comparative Example 1 A magnetic tape of the present invention was produced in exactly the same manner as in Example I, except that glass beads having an average particle diameter of 1.3 mm were used instead of silicon nitride beads.

Comparative Example 2 A magnetic tape was produced in exactly the same manner as in Example 1, except that alumina pieces with an average particle diameter of 1.3 mm were used instead of silicon nitride beads.

Comparative Example 3 A magnetic tape was produced in exactly the same manner as in Example 1, except that zirconia balls having an average particle diameter of 1.3 inches were used instead of silicon nitride beads.

The results of examining the electromagnetic conversion characteristics and head wear amount of each magnetic tape in Example 41 and Comparative Example are as shown in the table below. The electromagnetic conversion characteristics were determined using a rotating head at a frequency of 4M
The dead end was measured, and Comparative Example 1 was expressed as OdB as a relative value. The amount of head wear was determined by measuring the amount of wear per hour using a method of measuring changes in the length of the head tip using an optical microscope.

As is clear from the results in item 1, it is clear that according to the method of the present invention, a magnetic tape with excellent electromagnetic conversion characteristics and less head wear can be obtained.

Patent applicant: Hitachi Maxell, Ltd.

Claims (1)

[Claims] (1) Prepare a magnetic paint by mixing a paint composition containing a metal magnetic powder and a non-magnetic powder with a Mohs hardness of 6 or more using a high-speed media stirring type mill, and apply this paint onto the base. A method for manufacturing a magnetic recording medium, characterized in that silicon carbide or silicon nitride is used as a medium in the high-speed medium stirring type mill.