JPS5841420A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To inhibit the charging, to improve the running stability and to reduce the output change by laying a coated film contg. carbon black and a fluorine- contg. lubricant on the rear side of a substrate having a magnetic layer. CONSTITUTION:A coated film contg. carbon black and a fluorine-contg. lubricant is laid on the rear side of a substrate for forming a magnetic layer. The thickness of the coated film is generally regulated to about 0.05-5mum, and vinyl chloride-vinyl acetate copolymer resin or the like is used as a binder for forming the coated film on the substrate. The preferred amount of the carbon black is 40-60wt% of the total amount of the carbon black and the binder resin, and that of the lubricant is 0.5-5pts.wt. per 100pts.wt. carbon black.

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, mainly from the viewpoint of improving the winding characteristics or running stability of magnetic tape, it has been common practice to provide a coating film containing carbon black or carbon black and fatty acid ester on the back side of a base film such as a polyester film having a magnetic layer. However, it still cannot be said to be satisfactory in terms of reducing output fluctuation, which is the ultimate goal.

It is also possible to run a substrate, such as a polyester film in particular, over a rotating can via rollers, and apply Co to this under vacuum.
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, even if the conventional back coating film is provided, the output fluctuation will not decrease due to the following peculiar phenomenon. showed little 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 that the output fluctuation increases significantly, but even if the conventional back coating film containing carbon black is provided to solve this problem, sufficient antistatic effect cannot be obtained, and fatty acid ester has a low Because it volatilizes during vacuum deposition at the boiling point, there is almost no effect when used in combination with carbon black, so it has not been possible to significantly reduce output fluctuations.

As a result of intensive study in view of the above circumstances, the inventors found that
When a coating film containing carbon black and a fluorine-based lubricant was formed in advance on one side of a substrate such as a polyester film, and a magnetic metal vapor-deposited film was provided on the other side each time, the above-mentioned fluorine-based lubricant was coated. Because it has a higher boiling point than lubricants such as fatty acid esters and other silicone oils, it does not volatilize during vacuum deposition, and its excellent lubricating function and the conductive function of carbon black reduce the influence of secondary electrons during vacuum deposition. It has been found that this effectively suppresses charging due to slip caused by film elongation, and significantly contributes to reducing output fluctuations.

Further, according to the back coating film having the above structure, -I is used as the magnetic layer.
- It is not limited to those provided with a magnetic metal vapor deposited film as described above, but can also combine magnetic powders such as ferromagnetic metal or alloy powders such as γ-Fe 20g powder, Co-containing 1-Fe 20g powder, and α-Fe powder. It has also been found that even when a general magnetic layer such as one made of a magnetic resin is provided, running stability during recording and reproduction is significantly improved, and output fluctuations can be reduced from this point of view as well.

As described above, the magnetic recording medium of the present invention is characterized in that a coating film containing carbon black and a fluorine-based lubricant is provided on the back surface of a substrate having a magnetic layer, and according to this, output fluctuations can be prevented. It is possible to provide a magnetic recording medium with significantly improved characteristics.

As the carbon black used in this invention, one having an average particle diameter of 5 μm or less is suitable, and any of the various types of reprinted carbon black can be used. Specific examples of commercially available products include Ketjen Black EC manufactured by Lion Akzo, Black Pearl L1 manufactured by Cabot, Sheath 5H manufactured by Tokai Electrode, and H manufactured by Asahi Carbon.
5-500, product name H-600 manufactured by Mitsubishi Kasei Corporation, and the like.

The fluorine-based lubricant used in this invention is liquid or semi-solid at room temperature, and is generally characterized by a higher boiling point than silicone-based lubricants.

Typical chemical structural formulas include Fa Fa, but any of various commercially available products can be used without being limited to the above. Examples of commercially available products include Talitex (trade name) manufactured by DuPont, Fomblin (trade name) manufactured by Montegisson (all are perfluoroalkyl polyethers), and Dyfloil (polytrichlorotrifluoroethane) manufactured by Daikin Industries.

The thickness of the coating film containing carbon black and fluorine-based lubricant 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, polyvinyl butyral resin, polymethyl methacrylate resin, acrylonitrile-butadiene-styrene copolymer resin, polystyrene resin, vinyl chloride-vinyl acetate copolymer resin, Examples include polyurethane resin.

Carbon black accounts for 20% of the total amount with the binder resin above.
~80% by weight, preferably 40~60% by weight, and the fluorine-based lubricant contains carbon black 1
0.1 to 20 parts by weight, preferably 0.00 parts by weight.
The amount is preferably 5 to 5 parts by weight.

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

Example: V
60 parts of YHI ((trade name manufactured by LJ, C, C; vinyl chloride/vinyl acetate copolymer resin), Ketjenblack EC (
40 parts of Carbon Bra Tsuku (mentioned above), 1 part of Fonpurin (fluorinated lubricant mentioned above), 1 part of methyl isobutyl ketone
A paint consisting of 50 parts of toluene and 150 parts of toluene was applied to a dry thickness of 0.5 μm. Next, Co /
N1 weight ratio is 8/2 and coercive force is 500 mm) I? Stead's magnetic metal vapor deposited film is applied to the other side of the base film.
．． It was formed to have a thickness of 1 μm. Thereafter, it was cut into 1/2 inch width to obtain the magnetic tape of the present invention.

Comparative Example 1 Except that no fluorine-based lubricant was used in the paint components.
A magnetic tape was produced in the same manner as in the example.

Comparative Example 2 A magnetic tape was produced in the same manner as in Example, except that one part of n-butyl stearate was used instead of the fluorine-based lubricant in the paint components.

-I- Load each magnetic tape of Examples and Comparative Examples into a video tape recorder VT-8000 (manufactured by Hitachi),
The results of examining the output fluctuations after running 300 times at 40° C. and 80% RH are as shown in the following table. Furthermore, before performing vacuum deposition, the surface electrical resistance and friction coefficient of the coating surface of the polyester base film on which each coating was formed 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 509 cm between a pair of electrodes spaced 1 cm apart.
The resistance value was investigated when a voltage of

As is clear from the above table, it can be seen that the magnetic tape of the present invention exhibits significantly small output fluctuations during recording and reproduction.

Claims (1)

[Claims] (1) A magnetic recording medium characterized in that a coating film containing carbon black and a fluorine-based lubricant is provided on the back surface of a substrate having a magnetic layer.