JPS5841425A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To enhance the antistatic properties and lubricity by laying a coated film contg. powder of a linear conjugated high molecular substance and a fatty acid on the rear side of the substrate. CONSTITUTION:Powder of a linear conjugated high molecular substance having <=5mum average particle size and a 12-18C fatty acid such as lauric acid, palmitic acid or stearic acid are coated onto the rear side of a substrate having a magnetic layer with a resin binder. The high molecular substance is prepared by polymerizing acetylene or butadiyne which is conjugated diacetylene in the presence of Ziegler catalyst, has about 0.5-5 million average mol.wt., and is expressed by a formula -(CH)n-.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic recording medium such as a magnetic tape, in which a coating film having electrical conductivity and lubricating properties is provided on the back surface of a substrate having a magnetic layer.

Conventionally, it has been common practice to provide a coating film containing carbon black on the back surface of a base film such as a polyester film having a magnetic layer, mainly from the viewpoint of improving the winding characteristics or running stability of magnetic tape. This could not be said to be fully satisfactory in terms of the final objective of reducing output fluctuations.

In addition, a substrate such as a polyester film is run on a rotating can via rollers, and then α
In a magnetic recording medium having a magnetic metal vapor deposited film made by heating and vapor depositing a highly magnetic metal such as Ni, the following peculiar phenomenon shows that even if the conventional back coating film is provided, output fluctuations will not be reduced. It showed almost no effect.

In other words, in this type of magnetic recording medium, the base film is easily charged due to the influence of secondary electrons from the evaporation source, and the film elongates due to thermal expansion, causing slippage due to the speed difference between the rotating can and the traveling film. This can cause electrical charging, and when such electrical charging occurs, the running film tries to stick to the rotating can, which inevitably causes vertical wrinkles in the film, and when a magnetic metal vapor deposited film is formed on this film, There is a problem in which the output fluctuation increases significantly, but even if the conventional back coating film containing carbon black is provided to solve this problem, it does not show a sufficient antistatic effect and greatly reduces the output fluctuation. It didn't reach that point.

In view of the above circumstances, the inventors have conducted extensive studies and found that
Preliminary coating on the surface of a substrate such as a polyester film
When a powder made of a linear conjugated polymer substance represented by e-CH+n or a coating film containing the same and a fatty acid was formed, and a magnetic metal vapor-deposited film was provided on the other side of the powder, the above-mentioned specific result was obtained. Polymer materials have very good conductivity and relatively good lubricity, and this lubricity is further enhanced by the combined use of fatty acids, so secondary We have discovered that this effectively suppresses charging due to the influence of electrons and slippage caused by film elongation, and greatly contributes to reducing output fluctuations.

Further, according to the back coating film having the above-mentioned structure, the magnetic layer is not limited to the one provided with the above-mentioned magnetic metal vapor deposited film, but can also be made of γ-Fezes powder, Q-containing γ-Fe 20a powder, or α-Fezes powder.
Even when a general magnetic layer is provided, which is made by binding ferromagnetic metal such as Fe powder or magnetic powder such as alloy powder with a binder resin, the running stability during recording and reproduction is improved due to its good lubricity. It was found that this was a significant improvement, and from this point of view it was also possible to reduce output fluctuations.

As described above, the gist of the magnetic recording medium of the present invention is that a powder made of a linear conjugated polymer substance represented by +CH+ or a coating film containing the same and a fatty acid is provided on the back surface of a substrate having a magnetic layer. According to this, it is possible to provide a magnetic recording medium with significantly improved output fluctuation.

The linear conjugated polymer substance used in this invention is
It is generally produced by polymerizing butadiyne, which is acetylene or conjugated diacetylene, under a Ziegler catalyst, and has an average molecular weight of about 500,000 to 5,000,000, and an average particle size of 5.
It is preferable that the thickness be less than μ. Since the conductivity of this type of polymer substance decreases due to oxidation, it is preferable that the degree of oxidation of unsaturated bonds is suppressed to 1% or less of the total.

On the other hand, if an impurity such as AsF5 is mixed with this substance, the conductive function is enhanced, so the presence of such an impurity is particularly important in this invention. It's a good thing.

Even when a powder made of such a linear polymer substance is bound alone to a binder resin to form a back coating film, it has a better coating than a conventional coating film containing carbon black. It provides film strength, and its excellent conductivity and relatively good lubricity effectively prevents charging during vacuum deposition. It also provides good running stability during recording and playback, and improves output. Thickness (contributes to the reduction of fluctuations).

The fatty acid used in this invention further improves the strength and lubricity of the coating film when used in combination with the powder made of the above-mentioned polymeric substance, and provides even better results in reducing output fluctuations. Such fatty acids include those having 12 to 1 carbon atoms, such as lauric acid, valmitic acid, and stearic acid.
8 fatty acids are particularly preferred.

The thickness of the coating film containing the polymer substance or the polymer substance and fatty acid is generally about 0.05 to 5 μm. As a binder resin used to form such a coating film on a substrate, it is generally preferable to use a binder resin that has low adhesion to the magnetic layer, especially the magnetic metal vapor deposited film. Of course, the resin may also have the adhesive properties lowered by other additives.

Specific examples of the binder resin include cellulose resin, polyvinyl chloride resin, and polyvinyl butyral resin.

Examples include polymethyl methacrylate resin, acrylonitrile-butadiene-styrene copolymer resin, polystyrene resin, vinyl chloride-vinyl acetate copolymer resin, and polyurethane resin.

The polymeric substance accounts for 20 to 20% of the total amount with the binder resin described above.
The amount of fatty acid is preferably 80% by weight, preferably 40 to 60% by weight, and the fatty acid content is 0 to 20 parts by weight, preferably 0.5 to 5 parts by weight, based on 100 parts by weight of the polymeric substance. It is good that it is done.

Next, examples of this invention will be described. In the following, parts shall mean parts by weight.

Example 1 On one side of a 10μ thick polyester base film, V
YHH (trade name manufactured by U, C, C Company; vinyl chloride-vinyl acetate copolymer resin) 60 parts, linear conjugated polymer substance mono-derived from acetylene (average molecular weight: 1 million, average particle diameter 1 μ) 40 parts 150 parts of methyl isobutyl ketone and 150 parts of toluene to a dry thickness of 0.5 parts.
It was painted so that it became μ. Next, place the rotating can in the vacuum system at 10≠ so that the coating surface contacts this can.
A magnetic metal vapor deposited film having a Go/Ni weight ratio of 8/2 and a coercive force of 500 oersted was formed on the other side of the base film to a thickness of 0.1 μm while running at a speed of .

The magnetic tape of the present invention was obtained by cutting it into 1/2 inch width pieces.

Example 2 A magnetic tape was produced in the same manner as in Example 1, except that 1 part of valmitic acid was further blended into the paint components.

Comparative Example Instead of the linear conjugated polymer substance in the paint component, US-
A magnetic tape was produced in the same manner as in Example 1, except that 40 parts of soo (trade name, carbon black, manufactured by Asahi Carbon Co., Ltd.) was used.

Each of the magnetic tapes of Examples and Comparative Examples was loaded into a videotape recorder VT-goon (manufactured by Hitachi), and
The results of investigating the output fluctuations after running 300 times at °C and 180% RH were as shown in Table 1.Also, before vacuum deposition, the polyester base on which each coating was formed The surface electrical resistance and friction coefficient of the above-mentioned coated surface of the film were investigated, and the results are also listed in the following table.

The surface electrical resistance was determined by hanging the test film with a tension of 502 between a pair of electrodes spaced 1 cm apart.
The resistance value was determined when a voltage of 0.00 mm was applied, and the friction coefficient was determined by the rotating drum method.

As is clear from the above table, the magnetic tape of the present invention has small output fluctuations during recording and reproduction.

Claims (1)

[Claims] (1) A magnetic recording medium characterized in that a powder made of a linear conjugated polymer substance represented by +CH+ or a coating film containing the powder and a fatty acid is provided on the back surface of a substrate having a magnetic layer.