JPH0664734B2 - Alignment treatment device for magnetic recording media - Google Patents

Description

TECHNICAL FIELD OF THE INVENTION The present invention relates to an alignment treatment device for a magnetic recording medium, and more specifically, an alignment treatment that enables stable running of the magnetic recording medium in the alignment treatment device. Regarding a processing device.

[Technical Background of the Invention and Problems Thereof] A magnetic recording medium is composed of a substrate such as a polyethylene terephthalate film, and a magnetic layer in which a magnetic coating is formed by coating on the surface of the substrate.

The magnetic recording medium is manufactured generally as follows. That is, first, magnetic powder and various additives are blended to prepare a magnetic paint, which is applied to a film. While the magnetic particles in the magnetic coating material applied to the film are in a movable state, the film is then transferred to the alignment treatment device. And
In the alignment treatment device, the film is passed through the magnetic field generated by the magnetic field generating means, and the film is also dried.
Thus, the magnetic particles in the magnetic paint are oriented and fixed in the magnetic field direction, the squareness ratio in the orientation direction is increased, and the magnetic characteristics are improved. Then, the film is subjected to, for example, calendering to smooth the surface, and the magnetic recording medium is completed.

By the way, in the conventional orientation treatment, it was general to orient the acicular magnetic particles in the longitudinal direction of the coating film surface.

However, recently, in order to improve the recording density of the magnetic recording medium, a vertical alignment treatment for orienting magnetic particles in a direction perpendicular to the medium surface has been proposed.

Among these proposals, for example, in the vertical alignment treatment disclosed in JP-A-55-163633, JP-A-58-58246, and JP-A-58-222446, magnetic particles were aligned in the vertical alignment treatment. Drying / curing treatment is required for the purpose of increasing the viscosity of the coating film in a magnetic field in order to fix the orientation state. Then, in the vertical alignment treatment, the section of the magnetic field applied to the magnetic particles must be made longer than in the case of the conventional in-plane longitudinal alignment treatment.

In the above-described alignment treatment apparatus in which the magnetic field application section is long, it is necessary to provide a guide roll or the like to assist the movement of the film so that the film can stably move in the alignment treatment apparatus.

As described above, in the above vertical alignment treatment, the apparatus used for the vertical alignment treatment requires a new configuration, unlike the apparatus used for the conventional in-plane longitudinal orientation treatment, which not only improves the magnetic field generating means. The film running system must also be improved.

[Object of the Invention] An object of the present invention is to provide an alignment treatment device for a magnetic recording medium that enables stable running of the magnetic recording medium in the alignment treatment device.

[Summary of the Invention] The present inventor has found that, in an alignment treatment device such as a vertical alignment treatment device in which a magnetic field is applied for a relatively long period, the film is generated even in a magnetic field formed by a magnetic field generation unit of the alignment treatment device. By arranging a guide roll that rotates at the same peripheral speed as the running speed or a guide roll consisting of a free roll with low friction, it is possible to assist the running of the film in the magnetic field section over a long distance. I tried an experiment.

As a result, in the magnetic field formed by the magnetic field generating means,
When a metal roll such as chrome-plated steel, aluminum, stainless steel, titanium alloy, etc., which has been conventionally used in the manufacture of magnetic recording media, is installed, the rotation of the roll will be strongly damped and the roll will function normally. It has been found that the film will not rotate and it will interfere with the running of the film.

The present inventor has investigated the cause of strong braking that hinders the smooth rotation of the above-described metal guide roll, and when the guide roll rotates in a magnetic field, the guide roll is affected by the magnetic field and enters the roll. It was found that eddy currents that generate torque in the direction opposite to the rotation direction are generated, which increases the rotation torque of the roll and makes the rotation of the roll heavy.

Therefore, when the present inventor uses a non-metal roll that is not affected by a magnetic field as the guide roll, the braking applied to the rotation of the roll becomes negligibly small, and the guide roll rotates normally to perform magnetic recording. The present invention has been completed by finding the fact that a medium film can be stably run.

That is, the present invention is characterized in that the guide roll is a non-metal roll in the alignment treatment device for a magnetic recording medium.

First, the magnetic field generating means is not particularly limited as long as it can be applied to the orientation treatment of the magnetic recording medium.

For example, as the magnetic field generating means, an electromagnet, a permanent magnet, or a combination thereof can be used. Further, in the alignment treatment device of the present invention, the magnet may be integrated to form a single magnetic field section, or the magnet may be divided to form a plurality of magnetic field sections.

Next, the guide roll in the present invention assists the running of the magnetic recording medium, for example, the film, and is arranged in the running path of the film. Then, as shown in the figure, the traveling path of the film 1 is set so as to pass through the gap between the magnetic field generating means 2a and 2b. Therefore. Guide roll 3
Is also arranged between the magnetic field generating means 2a, 2b. The guide roll in the present invention is a non-metal roll having a configuration described later,
The non-metal roll 3 is preferably arranged not only between the magnetic field generating means 2a and 2b but also within a range where the magnetic field H generated from the magnetic field generating means 2a and 2b influences. In particular, when a plurality of magnetic field sections are provided, it is advisable to dispose a non-metal roll, which will be described later, between the magnetic field sections.

Next, the guide roll in the present invention is a non-metal roll. The non-metal roll as referred to in the present invention means a roll whose electric conductivity as a whole of the guide roll is significantly smaller than that of a normal metal. For example, the electrical conductivity of ordinary metal is 10 ⁴
To 10 ⁵ Omega ^{- 1} m ^{- 1} about a but, the electric conductivity of resins suitable as a material for the guide roll of the present invention is 10 ² to 10 ^{- 1
8 Ω -} is about ^{one - 1} m. The electric conductivity of the whole non-metal roll in the present invention is preferably a low value of about 1/100 or less of that of ordinary metals.

As described above, the non-metal roll of the present invention, which has a remarkably small electric conductivity as compared with a normal metal, has an extremely small effect of the magnetic field even if it is arranged in a magnetic field, and therefore the generation of eddy current is greatly suppressed.

The guide roll of the present invention is mostly made of a non-metal material having a low electric conductivity, but even a metal-non-metal composite material in which a metal is contained in a non-metal material has a higher electric conductivity than a normal metal. If it is extremely low, it can be used.

The point is that the non-metallic roll of the present invention may be any roll that is not affected by the magnetic field, and the material of the non-metallic roll of the present invention does not necessarily have to be made of a non-metallic material.

The material constituting the non-metal roll as described above,
For example, various glasses such as quartz glass, soda-lime glass, lead glass, borosilicate glass, aluminosilicate glass; various oxide ceramics such as alumina, magnesia, zirconia, spinel, mullite, lithia, titanium oxide, aluminum nitride, silicon nitride. , Various nitride ceramics such as titanium nitride, various ceramics such as carbide ceramics such as silicon carbide; phenol resin, epoxy resin, unsaturated polyester resin, silicon resin, polypropylene, polyamide, acetal resin, polycarbonate, polyethylene terephthalate, etc. Non-metallic materials such as resins; various composite materials such as those in which glass fibers are filled and reinforced with these resins, and those in which carbon fibers are filled to provide strength and appropriate conductivity to prevent frictional electrification; That.

Examples of the metal-nonmetal composite material include various oxide cermets, carbide cermets, silicide cermets, nitride cermets, metallized ceramics, metallized resins, metal fiber filled reinforced resins and the like.

In the case of resin or the like among the above-mentioned materials, it is effective because the electric conductivity is extremely low, but in such a case, for the purpose of preventing frictional electrification by the film and the roll, a suitable amount on the guide roll surface. It is preferable to impart electric conductivity. As a method of imparting an appropriate electric conductivity to the guide roll surface, a method of applying a thin metal coating to the guide roll surface or a composite of a conductive material and a non-conductive material as seen in the above-mentioned example There is a way.

Further, among the above-mentioned materials, magnetic coating materials and materials having excellent solvent resistance and heat resistance in terms of drying treatment are preferable.

[Examples of the Invention] Example 1 Five guide rolls made of silicon carbide having a diameter of 3 cm were arranged in a magnetic field space having a length of 60 cm, a width of 20 cm and a height of 8 cm, which were formed by an electromagnet, and under the magnetic field of 4 kOe. The guide roll was driven and rotated at the same peripheral speed as the film speed described later.

A polyethylene terephthalate film coated with a magnetic paint containing barium ferrite ultrafine powder was run at a speed of 40 m / min and passed through the magnetic field for vertical alignment treatment. Note that hot air was blown to the film during the alignment treatment to perform the alignment treatment and the drying treatment at the same time.

During the orientation treatment, no abnormality was observed in the rotation of the roll and the running of the film, and the running of the film was stable.

Examples 2 and 3 Same as Example 1 except that a guide roll made of carbon-containing epoxy resin was used in Example 2 and a guide roll made of carbon-containing polyimide resin was used in Example 3 with the same dimensions as those of the guide roll of Example 1. Then, the alignment treatment was performed.

The rotation of the roll and the running of the film during the orientation process were performed well.

Comparative Examples 1 and 2 The alignment treatment was performed in the same manner as in Example 1 except that an aluminum guide roll was used as Comparative Example 1 and a stainless steel guide roll was used as Comparative Example 2.

As a result, in Comparative Example 1, the rotational braking of the roll was large, and the roll could not be driven and rotated at the same peripheral speed as the running speed of the film.

In Comparative Example 2, although the rotational braking on the roll was somewhat smaller than that in Comparative Example 1, it was difficult to drive and rotate the roll, and the film could not run smoothly.

[Effects of the Invention] As is clear from the above description, the alignment treatment apparatus of the present invention enables stable running of the magnetic recording medium in the alignment treatment apparatus. As a result, the magnetic recording medium including a series of manufacturing steps can be smoothly manufactured, and the productivity can be improved, so that its industrial value is great.

It is needless to say that the present invention is not only effective when applied to the vertical alignment treatment, but is also effective when applied to other alignment treatments such as in-plane alignment and oblique alignment.

[Brief description of drawings]

 The figure is a schematic view showing an example of an alignment treatment apparatus. 1: Film, 2a, 2b: Magnetic field generating means 3: Guide roll, H: Magnetic field

Claims (1)

[Claims] 1. An alignment treatment apparatus for a magnetic recording medium, wherein the guide roll is a non-metal roll.