JPS59198534A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve resistance to wear and corrosion by providing a synthetic resin protective layer which consists essentially of polyvinyl butyral resin and a moisture-curable type polyurethane resin and of which the weight ratio of the resins is a specific ratio value on a thin magnetic metallic layer. CONSTITUTION:A protective layer 5 consists essentially of a polyvinyl butyral resin and a moisture-curable type polyurethane resin and the weight ratio of both resins is 2:1-1:2. If the moisture-curable type polyurethane resin decreases off said range, the wear resistance of the protective layer is not enough and if the polyvinyl butyral resin decreases off said range, the corrosion preventive effect of the resulting protective layer is not enough. Such protective layer is formed by mixing the two resins at the prescribed weight ratio and coating the mixture by a known method. Since the moisture-curable type polyurethane resin is used, the curing progresses by absorbing the moisture in air if the protective layer is allowed to stand in the air and therefore there is the advantage of not requiring any special curing stage.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic recording medium provided with a protective layer having excellent magnetic properties and electromagnetic conversion characteristics.

Conventionally, so-called coating-type products have been widely used as magnetic recording media, which are made by coating a powdered magnetic material such as oxide magnetic powder, ferromagnetic metal, or alloy powder on a non-magnetic support by dispersing it in an organic binder. ing.

However, in recent years, demands for high-density recording have increased due to improvements in the data retention capacity of computers, longer recording times, and improved image quality for VTRs.
Metal thin film type magnetic recording media, in which the magnetic recording layer is a magnetic metal thin film formed by paper deposition methods such as ion plating or plating methods such as electroplating and electroless plating, are attracting attention and have been put into practical use. has been done.

These metal thin film type magnetic recording media allow the magnetic recording layer to be formed as an extremely thin layer compared to the so-called conventional coating type.
The electromagnetic conversion characteristics are very advantageous.

However, in general, magnetic recording bodies using thin magnetic metal as the recording medium mainly have the following three practical problems.

The first problem is that the frictional resistance between the recording/reproducing head (hereinafter referred to as bed) and the magnetic recording body support component material is large and the wear resistance is poor, causing scratches on the magnetic recording medium or the head. This is a point that can cause damage such as.

The second point is that magnetic metals are susceptible to corrosion due to environmental conditions, and corrosion causes the magnetic properties of the magnetic metals to deteriorate or disappear, or pinhole corrosion causes an increase in errors.

The third point is that magnetic recording media are susceptible to damage and corrosion due to impact forces and contamination during handling.

In order to improve the above-mentioned problems, methods for forming a protective film on metal thin film type magnetic recording media, surface treatment methods using plasma, or paper deposition in an atmosphere of a substance thought to improve the physical properties of the magnetic layer have been proposed. Methods such as conducting the process indoors have been considered, but at present, no excellent method has yet been found to simultaneously solve the three problems mentioned above.

Further, when forming a protective film, it was difficult to obtain a uniform film thickness, and there were problems with smoothness.

Furthermore, conventionally, in order to harden the protective layer, for example, epoxy resin (1 heat treatment was required, but heat treatment causes thermal deterioration of the non-magnetic support), which is not preferable. .

The purpose of the present invention is to form a magnetic recording layer with a protective film that does not require heat treatment and has particularly excellent wear resistance and corrosion resistance. An object of the present invention is to provide a metal thin film type magnetic recording medium.

According to research conducted by the present inventors, it has been discovered that the above object can be achieved by constructing the protective layer using a polyvinyl butyral resin and a moisture-curable polyurethane resin.

Constructing the protective layer using polyvinyl butyral resin has been attempted in conventional coating-type magnetic recording media, but the protective layer itself consisting of polyvinyl butyral resin alone does not have sufficient wear resistance. , it is unsuitable for metal thin film type magnetic recording media. Furthermore, although the protective layer itself, which is composed of moisture-curing polyurethane resin alone, has wear resistance, it is insufficient from the viewpoint of corrosion prevention. It is not suitable for recording media.

As mentioned above, the present invention uses a polyvinyl butyral resin and a moisture-curable polyurethane resin together to
It has effects that could not have been predicted in the past,
The magnetic recording medium of the present invention is a magnetic recording medium in which a magnetic metal thin film is provided on a support, and the main components are a polyvinyl butyral resin and a moisture-curable polyurethane resin on the magnetic metal thin film, and the weight ratio of these resins is l: A synthetic resin protective layer having a ratio of 2 to 2:/ is provided.

＠/ Figure is a cross-sectional view of an embodiment of the magnetic recording medium of the present invention, in which the surface of the support is coated with an underlayer, a magnetic layer 3, a non-magnetic layer, a magnetic layer 3, a non-magnetic layer, and a magnetic layer. Layer 3 and the left protective layer are sequentially laminated.

As the support, any material that is normally used in magnetic recording media can be used, but polyethylene terephthalate film is preferably used because it has heat resistance, excellent dimensional stability, and high tensile strength.

As the magnetic metal constituting the magnetic layer, iron, cobalt, nickel, rare metals, rare earth-based and other ferromagnetic metals, non-metals, oxides thereof, or combinations thereof are used.

The underlayer S and the nonmagnetic layer q are made of, for example, aluminum, titanium, tin, or an organic compound.

In the above explanation, a structure in which magnetic layers and non-magnetic layers are alternately laminated on a support is used as an example (- has been explained, but structures other than those described above may also be used, and the present invention provides a structure in which magnetic metal thin film layers are laminated on a support). It can be applied to any type of magnetic recording medium that has.

The protective layer S is mainly composed of polyvinyl butyral resin and moisture-curable polyurethane resin, and the blending ratio of both resins (
Weight ratio) is 2:/~/:2. If the amount of moisture-curing polyurethane resin falls outside of the above range, the abrasion resistance of the resulting protective layer will not be sufficient, and if the amount of polyvinyl butyral resin falls outside of the above range, the corrosion prevention effect of the resulting protective layer will be insufficient. It becomes insufficient. Such a protective layer can be formed by mixing both resins in a predetermined weight ratio and applying the mixture by a known method. Furthermore, since a moisture-curing polyurethane resin is used, when left in the air at room temperature, curing progresses by absorbing moisture in the air, so there is also the advantage that no special curing process is required.

Of course, in order to accelerate curing, heating may be performed at a temperature within θ°C above room temperature.

Examples are given below to more specifically illustrate the present invention.

Example 1 3 on a 6 μm thick polyethylene terephthalate film
Provide a 00X thick aluminum vapor deposition layer, then vacuum! ;
X/0-! ; Using an alloy in which the weight ratio of cobalt and nickel is g to y at Torr, oblique evaporation was performed so that the incident angle was poo with respect to the film normal, and the film thickness was defined as gooX.

Furthermore, the above operation was repeated twice to produce a magnetic tape having a total of 6 vapor deposited layers. A sample was prepared by applying a surface treatment agent having a weight ratio of polyvinyl butyral to moisture-curable urethane of 75% and a resin concentration of 75% to the thus obtained magnetic tape using a gravure method.

Example U The same procedure as in Example 1 was carried out, except that the resin weight ratio of the surface treatment agent was polyvinyl butyral:moisture-curing urethane=/:/.

Example 3 A magnetic tape was produced in the same manner as in Example.

However, the resin weight ratio of the surface treatment agent was polyvinyl butyral:moisture-curing urethane-2:/.

Comparative Example/A magnetic tape was produced in the same manner as in Example/, except that the surface treatment with polyvinyl butyral and moisture-curing urethane was not performed.

Comparative Example A magnetic tape was produced in the same manner as in Example, except that polyvinyl butyral was used as the surface treatment agent.

Comparative Example 3 A magnetic tape was produced in the same manner as in Example, except that moisture curing urethane was used as the surface treatment resin.

Environmental test (RI0) for Examples/~3 and Comparative Examples/~3
℃, e/θ% RT (at/on force), and the number of corrosion points per unit area was investigated, and the surface condition after repeated SOO cycles on a standard recorder/player was investigated. The table below shows the results of investigating the noise conditions during driving.

As is clear from the second measurement results, the present invention provides a metal thin film type magnetic recording medium with extremely excellent corrosion resistance and significantly improved wear resistance and runnability. It was confirmed that this effect lasted for a long time.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an embodiment of the magnetic recording medium of the present invention. ／・・・・・・・・・・・・Support S・・Underlayer 3・・・・・・・・・・Magnetic layer q・・・・・・・・・・...Nonmagnetic layer left...Protective layer Patent applicant: Dai Nippon Printing Co., Ltd. Representative Patent attorney: Atsumi Konishi

Claims (1)

[Claims] (1) In a magnetic recording medium in which a magnetic metal thin film is provided on a support, the main components on the magnetic metal thin film are a polyvinyl butyral resin and a moisture-curable polyurethane resin, and the weight ratio of these resins is /:2 to 2:l. A magnetic recording medium provided with a synthetic resin protective layer.