JPH038111A - Magnetic tape - Google Patents

Abstract

PURPOSE:To obtain a magnetic tape excellent in corrosion resistance by specifying the eluted amt. of acid content in the powder incorporated into a back coating material to be used to form a back coating layer. CONSTITUTION:The eluted amt. of acid content in the powder in the back coating material used for the back coating layer is specified to <=500ppm. Since the powder to be incorporated into the back coating layer 4 is subjected to surface treatment such as acid washing to improve its dispersibility in the coating material and adhesion property to a binder, it is supposed that a small amt. of the acid remains in the powder and promotes corrosion in the magnetic recording layer. Therefore, it is required that the eluted amt. of acid reamining in the powder is <=500ppm.

Description

[Detailed description of the invention] [Industrial application fields] The present invention relates to a ferromagnetic metal thin film magnetic tape.

More particularly, the present invention relates to a magnetic tape having an improved bank coat layer.

[Prior Art] Magnetic recording media that have been in common use have been made by coating a magnetic layer mainly consisting of acicular magnetic powder and a polymeric binder on a non-magnetic substrate to form a magnetic layer. It is a coating type magnetic recording medium.

Currently, there is a trend toward higher density magnetic recording and reproducing devices, and there is a demand for magnetic recording media with excellent short wavelength recording characteristics.

However, there are limits to the improvement of short wavelength recording characteristics in coated magnetic recording media. On the other hand, metal thin film type magnetic recording media, in which a ferromagnetic material mainly composed of Co is formed on a non-magnetic substrate by a so-called physical vapor deposition method such as vacuum evaporation, sputtering, or ion blating, have a magnetic layer. Since no non-magnetic binder is mixed in, it is possible to obtain an extremely high residual magnetic flux density, and since the magnetic layer can be formed extremely thin, it has high output and excellent short wavelength response. Enjoy the benefits of being there.

Due to this feature, thin film magnetic recording media have recently become the mainstream of magnetic media.

Among such thin-film magnetic recording media, magnetic tape is required to have high running durability because it is constantly in sliding contact with magnetic heads, guide pins, and the like. In the case of audio tapes, this is dealt with by roughening the base film surface, but
Standard videotape, high-grade videotape, metal videotape for 8mm VTRs, and as tape grades increase, smoothness of the base film is required for high S/N1 and high recording density, and magnetic recording layer is required to improve running durability. The opposite problem is dealt with by providing a back coat layer made of carbon, various fillers, and binders.

Particularly in high recording density magnetic tapes having a magnetic recording layer made of a ferromagnetic metal thin film, an ultra-smooth base film with poor running properties is used, so the formation of a back coat layer is essential.

[Problems to be Solved by the Invention] However, since the magnetic layer is binder-free and comes into direct contact with the outside, it has the disadvantage of being susceptible to corrosion.

Therefore, various anti-corrosion techniques have been devised (see, for example, Japanese Patent Laid-Open No. 81-39218), and the corrosion resistance of the magnetic layer under high humidity conditions and a corrosive gas atmosphere λ has been greatly improved.

However, the effect is still not enough, and it is relatively /I
Even if stored in an If'fp environment, corrosion will gradually progress,
Problems such as corrosion products causing head clogging remain.

Surprisingly, it has been discovered that even if anti-corrosion measures are taken for the magnetic layer, the cause of the corrosion of the magnetic layer still lies in the back coat layer.

Accordingly, an object of the present invention is to provide a magnetic tape having excellent durability and having a bank coat layer that hardly corrodes the magnetic layer.

[Means for Solving the Problem] In order to achieve the above [1], in the present invention, a ferromagnetic metal thin film magnetic recording layer is formed on the surface of a non-magnetic substrate,
In a magnetic tape having a back coat layer formed on its back surface, the acid component in the powder used for the back coat paint for forming the back foot layer contains aJ elution [1 m = 5001) I) m (μg/ g) Provide a magnetic tape characterized by the following:

[Function] As mentioned above, by setting the total soluble acid component in the powder used in the bank coat paint for forming the bank coat layer to 500 ppm (μg/g) or less,
The corrosion resistance of the magnetic tape can be improved, and in particular, the corrosion resistance during storage can be significantly improved.

Since magnetic tape is constantly in sliding contact with magnetic heads, guide pins, etc., a high degree of running durability is required.

In particular, in high-density magnetic tapes whose magnetic recording layer is a ferromagnetic metal thin film, carbon,
It is essential to provide a bank coat layer made of powder such as calcium carbonate and a binder. The powder in these back coat layers is subjected to surface treatments such as pickling to improve dispersibility in the paint and adhesion to the binder, so there is a possibility that acid components may be mixed in. be. In particular, carbon black contains some amount of 41-organic acid, sulfuric acid, nitric acid, etc. derived from the raw material stone /111. It is believed that these residual acid components in the powder accelerate corrosion of the magnetic recording layer, so the total soluble content of the residual acid components in the powder needs to be 5'OOpl)m or less. . Further, since the residual acid component is present in the carbon black in IE, the soluble content of the acid component in the carbon black is preferably 400 ppm or less. Furthermore, among the residual acid components, the organic acid component in particular has a negative effect on head clogging, so the soluble content of the organic acid component in the gold powder and carbon black is 50 pp each.
m, 401) pm or less.

As a method for measuring the eluted content of the residual acid component in the powder, for example, the powder is washed with water or hot water, and the acid component eluted in the washing water is titrated by a conventional method or by ion chromatography. It consists of measuring with an automatic analyzer such as a graphimeter. The residual acid components that are not eluted with the washing water are firmly bound in the powder, so they are not easily eluted with respect to corrosion of magnetic metals.
j, the ability to do 1'iJ is extremely small.

ii') Elution of the residual acid component in the powder (iEt) If the elution content (iEt) is greater than the above-mentioned limit value, it is possible to reduce the elution content of the residual acid component by neutralizing the powder, etc. I agree.

J, [, the magnetic recording layer formed on the body is Co1Fe1
Filling with ferromagnetic metals and alloys such as N1, Co-Ni alloy, Co-Cr alloy, Co-P alloy, Co-N1-P alloy, ion blasting, sputtering, ring,
The base is 1° by conventional means.

It can be formed by a method such as coating.

The magnetic tape of the present invention includes polyester film,
Audio tapes, VTR tapes, r) AT tapes based on synthetic resin films such as polyimide films,
Various forms of backcoat layers are included, such as streamer tape.

[Example] Hereinafter, the present invention will be explained in detail with reference to Examples.

A polyester film with a thickness of 10 μm is vacuum vaporized ('?'
Place it in position A and place it in C under a vacuum of 10-6 torr.

The B□N12o alloy was heated and evaporated to form a 2000 mm thick CoNi ferromagnetic metal thin film layer on the polyester film. Next, the polyester film on which the ferromagnetic metal thin film layer was formed was set in a gravure coating device, and the back coat paint of Doki Shausei was applied on the side on which the ferromagnetic metal thin film layer was not formed, and after a drying process, A 1 μm thick back coat layer was formed on the surface on which the ferromagnetic metal thin film layer was not formed. The 1 town elution content of the Cr organic acid component in the carbon blank was 10 pl)m or less, and the total 5f elution content of the acid component was 1100 pp.

Back coat->2 Carbon black (A) 12. Ovt% Nitrocellulose 3.9wt% Polyurethane 2.3wt% Crosslinker
1.3vt% nclohexanone (solvent)
80. Next, apply this polyester film to rT [gravure coater]. Then, a rust preventive paint was applied onto the surface on which the ferromagnetic metal thin film layer was formed, and a rust preventive paint layer with a thickness of 50 mm was formed on the ferromagnetic metal thin film layer through a drying process. Thereafter, it was cut to a predetermined width to produce a magnetic tape having a cross-sectional structure as shown in FIG.

In place of the carbon brazing agent (A) used in the Examples, the organic acid component iiJ elution content i1 was 1100p.
A magnetic tape was produced in the same manner as in the example except that carbon black (B) containing 8,000 ppm of total acid component (soluble content) 4 was used.

Each magnetic tape produced as described above was assembled into an 8mm VTR cassette half with a 90-minute specification, and
Corrosion resistance was evaluated after being left for 30 days with the lid closed in a C180% RH atmosphere.

This evaluation is based on the deterioration rate of saturation magnetization (Ms) and the head adhesion after running 100 times (150 hours in total) on the actual machine.
11. The evaluation criteria for the amount of deposits on the head were based on four levels: ◎: almost none, ○: little, △: somewhat much, and ×: much. The results are shown in Table 1 below.

As is clear from the above results, the Ms deterioration rate of the magnetic tape of the present invention obtained in the Examples is smaller than that of the control magnetic tape obtained in the Comparative Examples, and there are fewer deposits on the head. From these results, it is understood that according to the present invention, a magnetic tape with significantly superior corrosion resistance can be obtained.

[Effects of the Invention] As explained above, when a bank coat layer is formed on the back side of a magnetic tape having a ferromagnetic metal thin film layer,
By controlling the soluble content of acid components in the powder used in the back coat paint for forming the back coat layer to 500 ppm or less, the corrosion resistance of the magnetic tape is improved, and in particular, the corrosion resistance during storage is significantly improved. can do.

[Brief explanation of drawings]

FIG. 1 is a partially enlarged sectional view showing an example of a magnetic tape obtained by the present invention. 1...Magnetic tape, 2...Polyester film. 3... CoNi magnetic layer, 4... Back coat layer. 5... Rust preventive layer

Claims (1)

[Claims] (I) A magnetic tape in which a ferromagnetic metal thin film magnetic recording layer is formed on the surface of a nonmagnetic substrate, and a back coat layer is formed on the back surface of the magnetic tape, in which the back coat layer is formed. 1. A magnetic tape characterized in that the total leached content of acid components in the powder used for a back coat paint is 500 ppm (μg/g) or less. (2) The soluble content of organic acid components among acid components is 50p
2. The magnetic tape according to claim 1, wherein the magnetic tape has a particle diameter of pm or less. (3) The total soluble content of acid components in the carbon black of the back coat paint is 400 ppm or less, and
2. The magnetic tape according to claim 1, wherein the soluble organic acid content is 40 ppm or less.