JPS5841429A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a recording medium having a vapor-deposited magnetic metallic film with superior antistatic and lubricating properties by laying a coated film contg. metallic powder and a fatty acid on the back side of a substrate. CONSTITUTION:Electrically conductive metallic powder such as aluminum powder, copper powder or stainless steel fiber and a 12-18 C fatty acid such as lauric acid, palmitic acid or stearic acid are coated onto the back side of a substrate having a vapor-deposited magnetic metallic film with a resin binder.

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 side of a substrate having a magnetic metal vapor deposited film.

A magnetic recording medium having a magnetic metal deposited film is generally produced by running a substrate such as a polyester film onto a rotating can via rollers, and then heating and depositing a highly magnetic metal such as Co or Ni onto the substrate under vacuum. ing. However, with this method, 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, which causes charging. When this electrical charge occurs, the running film tends 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, the output fluctuates significantly. There were drawbacks that were increasing rapidly.

As a result of intensive study in view of the above circumstances, the inventors found that
By forming a coating film containing conductive metal powder and fatty acid on one side of a substrate such as a polyester film in advance, and providing a magnetic metal vapor deposited film on the other side each time, the coating film has conductivity and lubricity. Because it has excellent sex,
Charging caused by secondary electrons during vacuum evaporation and slippage caused by film elongation are effectively suppressed.
Knowing that a magnetic recording medium with small output fluctuations can be obtained,
This led to the completion of this invention.

That is, the present invention relates to a magnetic recording medium characterized in that a coating film containing conductive metal powder and a fatty acid is provided on the back surface of a substrate having a magnetic metal vapor deposited film.

By the way, it is well known that in general magnetic tapes, a coating film containing carbon black and fatty acid ester is provided on the back surface of a base material having a magnetic layer in order to improve the winding characteristics or running performance of the tape. be. However, if such a known coating film is applied to the present invention, it is not possible to effectively prevent the occurrence of vertical wrinkles. The reason for this is that fatty acid esters, which have a lubricating effect, generally have a very low boiling point and easily volatilize during vacuum evaporation, so even if they are used in combination with carbon black, they cannot demonstrate their original function, and they rely exclusively on the conductive function of carbon black. This is because, inevitably, in this case, a sufficient antistatic effect cannot be obtained.

On the other hand, in the coating film according to the present invention, the conductive metal powder alone exhibits an excellent antistatic effect, and the fatty acid that is used in combination with the powder to give strength to the coating film is more effective in vacuum than the fatty acid ester. Since it is difficult to volatilize during vapor deposition and has excellent lubricity, its original lubricating function and the conductive function of the conductive metal powder work synergistically to reduce the charge during vacuum vapor deposition. This greatly contributes to reducing output fluctuations.

The conductive metal powder used in this invention includes aluminum powder, copper powder, stainless steel fiber, etc., and the average particle size thereof is 5μ or less, and needle-shaped ones such as stainless steel fiber have an axial ratio of about 5 to 50. Preferably. Even if these seven types of metal powders are included alone in a coating film, they lack coating strength, so this drawback can be avoided by using them in combination with fatty acids, and at the same time, by using their lubricity, vacuum evaporation Provides even better results in preventing static electricity. As such fatty acids, fatty acids having 12 to 18 carbon atoms such as lauric acid, palmitic acid, and stearic acid are suitable.

The thickness of the coating film containing conductive metal powder and fatty acid is generally 0.
．． It is about 0.05 to 5μ. 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 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.

The conductive metal powder is 20-8% of the total amount with the binder resin above.
The amount of fatty acid is preferably 0.1 to 20 parts by weight, preferably 0.5 to 5 parts by weight, based on 100 parts by weight of the conductive metal powder. It would be good if it was considered a department.

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

Example: On one side of a 10μ thick polyester base film, V
60 parts of YHH (product name manufactured by U, C, C; vinyl chloride-vinyl acetate copolymer resin), 40 parts of stainless fiber (average particle diameter 0.5μ, axial ratio 20), 1 part palmitic acid,
150 parts of methyl in butyl ketone and 150 parts of toluene
A coating material consisting of 1.5 mm was applied so that the dry thickness was 0.5 μm. Next, while running a rotating can in the vacuum system at a speed of 10 m7 so that the coated surface is in contact with this can, Co / N + weight ratio is 8/2 and coercive force 5 is applied.
A 0.00 oersted magnetic metal vapor-deposited film was formed on the other side of the base film to a thickness of 0.1 μm. Then, the tape was cut into 1/2 inch pieces to obtain the magnetic tape of the present invention.

Comparative Example Example except that 40 parts of l-18-500 (trade name: carbon black, manufactured by Asahi Carbon Co., Ltd.) and 1 part of n-butyl stearate were used instead of the stainless fiber and fatty acid in the paint components. A magnetic tape was produced in the same manner.

Each of the magnetic tapes of the above examples and comparative examples was loaded into a video tape recorder VT-8000 (manufactured by Hitachi), and
The results of examining the output fluctuations after running 300 times at 80% RH at 80% RH are as shown in the following table. 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 is determined by suspending the test film by applying a tension of 50y between a pair of electrodes with an interval of 1cIn, and examining the resistance value when a voltage of 500V is applied. was measured by the rotating drum method.

As is clear from the above table, in the magnetic tape of the present invention, the surface electrical resistance and friction coefficient of the polyester base film before vacuum deposition are small, and the output fluctuation during recording and reproduction is extremely small. I understand.

Patent applicant: Hitachi Maxell, Ltd. Agent: Patent Attorney: Motokuni Fu'-Ko

Claims (1)

[Claims] (1) A magnetic recording medium characterized in that a coating film containing conductive metal powder and a fatty acid is provided on the back surface of a substrate having a magnetic metal vapor deposited film.