JPH0467253B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] This invention relates to a magnetic tape having a metal magnetic layer.

[Background technology]

A magnetic layer made by coating metal magnetic powder such as metallic iron on a base film together with a binder has a much higher coercive force and residual magnetic flux density than those using oxide-based magnetic powder, making it an excellent material. Demonstrates excellent magnetic performance. Further, in the case of a magnetic tape in which a magnetic layer is formed by directly depositing metal on a base film, there is no need to use a binder, and the magnetic performance is further improved accordingly.

However, unlike those using oxide-based magnetic powder, magnetic tapes with such metal magnetic layers suffer from oxidative corrosion due to oxygen and water vapor in the air, causing their magnetic properties such as saturation magnetic flux density to deteriorate over time. There is a particular problem in that it is easy to do.

For this reason, in order to prevent such oxidative corrosion, methods of forming various organic films or oxide films on the surface of metal magnetic powders have been adopted. However, if the former organic film is used in a small amount, it is difficult to form a complete film, and if it is used in a large amount, the surface properties and wear resistance of the magnetic layer will be impaired. Further, the latter coating of ordinary metal magnetic powder oxide is not preferred because it inevitably lowers the saturation magnetization of the magnetic powder.

In addition, in the case of a magnetic tape provided with a vapor deposited layer,
Attempts have been made to provide a top coat layer containing a suitable rust preventive agent on top of the vapor deposited layer. However, if a large enough amount is applied to produce a rust-preventing effect, spacing loss with the head will occur, and the rust-preventive agent will be removed by sliding contact with the head, making it difficult to expect a sustained rust-preventing effect. .

[Purpose of the invention]

From the above viewpoint, the inventor has developed a magnetic tape having a metal magnetic layer that has highly improved stability of magnetic properties over time without impairing initial magnetic properties, surface properties of the magnetic layer, wear resistance, etc. The purpose is to provide.

[Summary of the invention]

As a result of intensive studies to achieve the above object, the inventor found that when a layer containing a volatile rust preventive agent is formed on the back side of a base film having a metal magnetic layer on the main surface, the magnetic properties become stable over time. The inventors discovered that it was possible to obtain a magnetic tape with highly improved properties, and came up with this invention.

As the base film used in this invention, any conventionally known base film such as a polyester film having a thickness of about 6 to 14 μm can be used. Further, the metal magnetic layer provided on the main surface of the base film may be a magnetic layer coated with metal magnetic powder together with a binder, or may be a vapor deposited layer of a magnetic metal or alloy. The effect of the present invention is particularly significant because the vapor deposited layer is prone to deterioration over time.
Also, among the metal magnetic layers, a deposited layer of Co metal or an alloy mainly composed of Co can be used in the present invention.

In order to form a layer containing a volatile rust preventive agent on the back side of a base film having a thickness of 6 to 14 μm on the main surface of which the magnetic layer is formed, an appropriate binder is usually used to form a paint containing the binder. A volatile rust preventive agent may be added and applied to the back surface. The above paint may be a back coat paint containing carbon black or other pigments to prevent static electricity and improve running stability.

Another method for forming a layer containing a volatile rust preventive agent is to first apply a back coat paint as described above to the back of the base film, and then apply the volatile rust preventive agent or its solution on this layer. It may be applied to impregnate the pores inside the layer.

The thickness of the layer containing the volatile rust preventive agent formed in this way is usually about 0.3 to 2.0 μm. In addition, the content of volatile rust preventive agent is as follows:
Generally 0.1 per 100 parts by weight of paint solids for layer formation
The amount is preferably about 5 parts by weight.

The above-mentioned volatile rust preventive agent may be one that can gradually volatilize at room temperature and exhibit a rust preventive function, and typical examples thereof include benzotriazole and dicyclohexylammonium nitrite.

〔Effect of the invention〕

As described above, the magnetic tape of the present invention has a layer containing a volatile rust preventive agent on the back side of the base film having a metal magnetic layer on its main surface. to prevent corrosion of the metal magnetic layer. If the rust preventive agent that has been transferred is scraped off by the magnetic head during running, the rust preventive agent will be transferred again when the tape is wound, and this process can be repeated many times, so the above corrosion prevention effect is reduced. Lasts forever.

In this way, unlike conventional magnetic tapes in which a top coat layer containing a rust preventive agent is provided on the surface of a metal vapor-deposited layer, the magnetic tape of the present invention can be expected to have a sustained rust prevention effect. The stability can be greatly improved. In addition, the conventional top coat layer has the disadvantage of causing spacing loss with the head when it is applied thickly.
The above-mentioned magnetic tape of the present invention does not have such drawbacks.

Moreover, since the magnetic tape of the present invention is provided with a layer containing a volatile rust preventive agent as a back coat layer, it is different from conventional magnetic tapes in which an organic film or an oxide film is formed on the surface of metal magnetic powder. There is no concern that the amount of saturation magnetization will decrease or that the surface properties or wear resistance of the magnetic layer will be impaired. In other words, without damaging the initial magnetic properties or durability properties,
It has the advantage of improving aging characteristics.

In addition, in this invention, a vaporizable rust preventive agent is selected in particular so that even if the adhesion between the tapes is poor during tape winding, the vaporization property is utilized to allow the vapor to remain between the tapes. This is because the corrosion prevention effect can be reliably and efficiently expressed.

〔Example〕

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

Example 1 80% by weight of Co and 20% by weight of Ni on one side of a 10 μm thick polyethylene terephthalate film
A metal vapor deposition layer with a thickness of 0.15 μm was formed. Next, on the opposite side of this film, the following back coat paint containing benzotriazole as a volatile rust preventive agent was applied and dried to a dry thickness of 1.0 μm, and the film was slit to a predetermined width. A magnetic tape was produced.

Carbon black 20 parts Red iron 10 parts Polyurethane 5 parts Nitrocellulose 3 parts Trifunctional isocyanate 2 parts Benzotriazole 1 part Cyclohexanone 30 parts Toluene 30 parts Comparative Example 1 Same as Example 1 except that benzotriazole was removed from the back coat paint. A magnetic tape was produced in the same manner.

Comparative Example 2 A magnetic tape was produced in exactly the same manner as in Example 1, except that one part of stearyldiethanolamine, a non-volatile rust inhibitor, was used instead of benzotriazole in the back coat paint.

Example 2 On one side of a 7 μm thick polyethylene terephthalate film, the following magnetic paint containing metal iron powder as metal magnetic powder was applied and dried to a dry thickness of 3 μm to form a magnetic layer.

Metallic iron powder 100 parts Vinyl chloride-vinyl acetate-vinyl alcohol copolymer 10 parts Polyurethane 10 parts Polyisocyanate 5 parts Cyclohexanone 120 parts Toluene 120 parts Carbon black 3 parts Alumina 4 parts Liquid paraffin 1 part Lauric acid 1 part Next, the above Example 1 except that one part of dicyclohexylammonium nitrite was used instead of benzotriazole on the opposite side of the film.
A back coat paint with the same composition as the dry thickness
The magnetic tape of the present invention was prepared by coating it to a thickness of 1 μm, drying it, and cutting it to a predetermined width.

Comparative Example 3 Example 2 except that dicyclohexylammonium nitrite was removed from the back coat paint.
A magnetic tape was produced in the same manner.

Each of the magnetic tapes obtained in the above Examples and Comparative Examples was stored under high temperature and humidity conditions of 60° C. and 90% RH, and changes in saturation magnetic flux density over time were examined. The results are shown in FIG. 1 for the magnetic tapes of Example 1, Comparative Example 1, and Comparative Example 2, and in FIG. 2 for the magnetic tapes of Example 2 and Comparative Example 3. Note that in both figures, the deterioration rate of the saturation magnetic flux density on the vertical axis is expressed by the following formula.

Deterioration rate = Bmo − Bmt / Bmo × 100 (%) Bmo: Initial saturation magnetic flux density Bmt: Saturation magnetic flux density after storage As is clear from both figures, the magnetic tape of this invention has excellent aging characteristics. I understand that.
It can also be seen that the effect of improving the aging characteristics is more pronounced in the case of the magnetic tape provided with the metal vapor deposited layer of Example 1.

[Brief explanation of drawings]

Fig. 1 is a characteristic diagram showing the change over time in the saturation magnetic flux density of each magnetic tape of Example 1, Comparative Example 1, and Comparative Example 2, and Fig. 2 is a characteristic diagram showing the saturation magnetic flux density of each magnetic tape of Example 2 and Comparative Example 3. FIG. 2 is a characteristic diagram showing changes over time.

Claims (1)

[Scope of Claims] 1. A magnetic tape characterized in that a layer containing a volatile rust preventive agent is formed on the back side of a base film having a metal magnetic layer on its main surface. 2. The magnetic tape according to claim 1, wherein the metal magnetic layer is a vapor-deposited layer of Co metal or a Co-based alloy.