JPS5841431A - 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 fluorine-contg. surfactant on the back side of a substrate. CONSTITUTION:Electrically conductive metallic powder such as aluminum powder, copper powder or stainless steel fiber and a fluorine-contg. surfactant which has a CF3 group and a hydrophilic group at both molecular terminals and is liq. or semisolid at ordinary temp. are coated onto the back side of a substrate having a vapor-deposited magnetic metallic film with a resin binder. The surfactant is CF3(CF2)nCO-OH, CF3(CF2)n-(CH2CH2O)m-H, CF3(CF2)nSO3H, CF3(CF2)n PO3H or the like.

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 manufactured 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 CO1Ni onto the substrate under vacuum. . 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
When a coating film containing conductive metal powder and a fluorosurfactant was formed on one side of a substrate such as a polyester film in advance, and a magnetic metal vapor-deposited film was provided on the other side each time, the coating film was Because it has excellent conductivity and lubricity, it effectively suppresses charging due to the influence of secondary electrons during vacuum deposition and charging due to slip caused by film elongation, resulting in a magnetic recording medium with small output fluctuations. Knowing this, I was able to complete this invention.

That is, the present invention relates to a magnetic recording medium characterized in that it is provided with a coating film including a thread having a magnetic metal vapor-deposited film.

By the way, in general magnetic tapes, it is already known that a coating film containing carbon black and fatty acid ester is provided on the back surface of a substrate having a magnetic layer in order to improve the winding characteristics or running performance of the tape. However, if such a known coating film is applied to the present invention, the occurrence of vertical wrinkles cannot be effectively prevented. The reason for this is
Fatty acid esters that have a lubricating effect generally have a very low boiling point and easily volatilize during vacuum deposition, so even if they are used in combination with carbon black, they cannot demonstrate their original function and must rely solely on the conductive function of carbon black. This is because, 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 exhibits an excellent antistatic effect even when alone, and the fluorine-based surfactant that is used in combination with the powder to give strength to the coating film is a fatty acid ester. It is less likely to volatilize during vacuum deposition than other metals, has excellent lubricity, and has the ability to uniformly disperse and bind metal powder.
Due to the synergistic effect of the original lubricating function and the conductive function of the conductive metal powder, charging during vacuum deposition is significantly suppressed and 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. This type of metal powder lacks coating strength even if it is included alone in a coating film, so this drawback can be avoided by using it in combination with a fluorine-based surfactant, while improving the lubricity and uniformity of the metal powder. Utilizing its dispersibility, it provides even better results in preventing static electricity during vacuum deposition.

Fluorine-based surfactants that play this role are compounds that have a CF3 group and a hydrophilic group at both ends of the molecule and are liquid or semi-solid at room temperature, and like general fluorine-based lubricants, silicone oil, etc. It has a higher boiling point than other lubricants and has a better lubricating function due to the fluorine atoms it contains, but it has a hydrophilic group at the end of the molecule and exhibits surfactant-like action. It is structurally and functionally distinct from fluorine-based lubricants.

Typical chemical structural formulas include, for example, a) CF
3 (CF2). C0OH.

o) CF3(CF2)n(CH2CH20)mH.

Seven examples include CF3(CF2)nSOaH1 =) CF3(CF2)nPO3H, but any commercially available product having a hydrophilic group or chemical structure other than the above may be used. An example of a commercially available product is Sumitomo 3 as perfluoroalkylcarboxylic acid.
Part name: Florado FC-26 manufactured by Company M; Part name: 70 Lardo FC-98 manufactured by Sumitomo 3M Company as a perfluoroalkyl carboxylate; Part name: Megafac F- manufactured by Dainippon Ink Company.
120, Asahi Glass Co., Ltd. product name Surflon S-111, same S
-113, perfluoroalkyl ethylene oxide adduct manufactured by Sumitomo 3M, part name FC-430, FC-
431, Dainippon Ink Co., Ltd. Part name Megafac F-14
2D, F-144D, etc., and as a perfluoroalkyl sulfonate, F-110 (trade name, manufactured by Dainippon Ink Co., Ltd.)
and so on. As mentioned above, these surfactants have a high boiling point and are difficult to volatilize during vacuum deposition, so that they can effectively exhibit their original lubricating function or dispersion binding function.

The thickness of the coating film containing the conductive metal powder and the fluorosurfactant 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 metal vapor deposited film. Of course, the resin may also have the adhesive properties lowered by other additives.

Specific examples of the binding 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, and polyurethane. Examples include resin.

The conductive metal powder is 20-8% of the total amount with the binder resin above.
The amount of the fluorine-based surfactant is preferably 0.1 to 20 parts by weight, preferably 0.1 to 20 parts by weight, based on 100 parts by weight of the conductive metal powder. 0.5～
It is preferable that the amount is 5 parts by weight.

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

Example One side of a polyester base film with a thickness of 10 μm
60 parts of yHH (product name manufactured by U, C, C Co., Ltd.: hinyl chloride-vinyl acetate copolymer resin), 40 parts of stainless fiber (average particle diameter 0.5μ, axial ratio 20), FC-430 (the above-mentioned fluorine-based interface) A coating consisting of 1 part of activator), 150 parts of methyl isobutyl ketone, and 150 parts of toluene was applied so that the dry thickness was 0□5μ.Next, the painted surface was brought into contact with a rotating can in the vacuum system. 10m/
The Co/Ni weight ratio is 8 while running at a speed of
A magnetic metal vapor-deposited film having a coercivity of 500 oersted and a coercive force of 0.1 μm thick was formed on the other side of the base film.

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

Comparative Example Example except that 40 parts of H8-500 (trade name, carbon black, manufactured by Asahi Carbon Co., Ltd.) and 1 part of n-butyl stearate were used instead of stainless steel fiber part FC-430 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. 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. Note that the surface electrical resistance is 5 cm for a pair of electrodes spaced apart by 1 crn.
(The test film was hung under a tension of 1 and the resistance value was investigated when a voltage of 500 V was applied. Also, the friction coefficient 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.

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Claims (1)

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