JPS58200424A - magnetic recording medium - Google Patents

Abstract

PURPOSE:To prevent the surface of a magnetic layer from causing trouble due to electrification without deteriorating magnetic characteristics, by interposing a thin metallic film as an electrically conductive layer between a coated magnetic film as the magnetic layer and a base film to reduce the electric resistance of the surface of the magnetic layer. CONSTITUTION:Al, Cr, Ni or the like is vapor-deposited on one side of a nonmagnetic plastic film base to form a metallic thin film having 0.01-0.1mum thickness as an electrically conductive layer having 1-10<6>OMEGA/? surface, resistivity. A magnetic layer is formed on the electrically conductive layer using a magnetic coating contg. magnetic powder, a binder, a dispersant, an antistatic agent, etc. Dropout due to static electricity is prevented during the preparation of the magnetic coating, the electric resistance of the surface of the magnetic layer is reduced to reduce electrification and to prevent dropout and noise, and the amount of the antistatic agent to be added to the magnetic layer can be reduced. Accordingly, the magnetic characteristics and sensitivity are improved.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic recording medium, and an object thereof is to provide a magnetic recording medium that prevents charging and has less dropout due to adhesion of dust and less noise due to discharge. .

In general, coating type magnetic recording media is prepared by preparing a magnetic paint that is dispersed in a total binder solution of oxide-based magnetic powder or metal magnetic powder.
This is coated on a polyester film, etc. to form a magnetic layer, and then subjected to operations such as smoothing, magnetic field orientation, drying, calendering, and cutting. Recording media tend to become electrically charged when the electrical resistance of the surface of the magnetic layer is large, and this electrical charging caused particles to form during the manufacturing process or during use, resulting in dropouts. The problem was that it generated noise.

Conventionally, in order to improve the drawbacks mentioned above, measures have been taken to prevent static electricity by incorporating non-magnetic powder such as carbon black and various surfactants into magnetic paints to completely reduce electrical resistance. It is being However, carbon black, which has good conductivity, has poor dispersibility, and when used in large quantities, it deteriorates the dispersibility of the magnetic paint and the surface properties of the magnetic layer, reduces the optical density of the magnetic powder, and causes problems when used in large quantities. On the contrary, V is the cause of noise generation, so there is a limit to its use.3. On the other hand, surfactants have similar limitations, such as their ineffectiveness unless the humidity is high, and their tendency to cause bleed errors (bleeding errors), which deteriorate the running properties of the magnetic recording medium, so it is not expected that the effect will be fully satisfactory. could not. It is also possible to knead carbon black or the like into the base film itself to lower the total resistance and make it difficult to charge; We cannot satisfy you.

In light of the above-mentioned situation, the present inventor has conducted detailed research in order to reduce the electrical resistance on the surface of the magnetic layer, and as a result, the inventors have previously applied vacuum evaporation, ion blating, sputtering, etc. to one side of the plastic film. forming a thin film,
If a magnetic paint is applied to the thin metal film, dropouts due to static electricity interference during the coating process will be prevented, and at the same time, the electrical resistance on the surface of the magnetic layer will be reduced, preventing electrification and reducing dropouts and noise. Moreover, by reducing the amount of antistatic agents such as carbon black added, the residual magnetic flux density (Br) and squareness ratio (B) of the magnetic recording medium can be improved.
r/Bs) and other magnetic properties as well as sensitivity properties, and arrived at the present invention.

That is, the present invention is characterized by combining a magnetic coating film and a base film.

The conductive layer can be formed by any known metal thin film forming method such as vacuum evaporation, ion solate ink, sputtering, or plating, and the thickness and surface resistance can be adjusted depending on the film formation rate, degree of vacuum, atmospheric gas, substrate Lhu degree, etc. do.

At this time, if the thickness (f-0) is less than 1 μm, the pressure (rtM pressure 150 to 260K) is equivalent to calendering of the magnetic coating film.
g/cm), J:ri crank enters, the electrical resistance of the metal thin film increases and becomes unstable, and conversely, o, 01
If the surface resistance is less than 1 μm, it is not possible to obtain a small metal thin film with a stable surface resistance, and if the surface resistance of the conductive layer is less than 106 Ω/2, the addition of carbon black in the magnetic coating cannot be completely reduced. Conversely, if the thickness is less than 1Q10, a stable metal thin film of 0.111 m or more cannot be obtained. l as a metal
L, Cu, Ti, Ni, etc. can be used, and if corrosion resistance is required in 11), Au, Or is preferable.

As the binder component of the magnetic paint, thermal i'iT plastic resins such as vinyl chloride copolymers, vinylitine chloride copolymers, cellulose resins, butyral resins, and polyurethane resins are suitable; Polyester resins and butadiene copolymers may also be used.

These binder components can be used alone or in combination of two or more types, and can also be used as epoxy resins.

It can also be used in a mixed form with thermosetting resins such as urethane prepolymers, polyisocyanates, phenolic resins, urea resins, and melamine resins.

As magnetic powder, 7-Fe2es, Fe3O4
, CrO2° cobalt-containing γ-1620s, cobalt-containing Fe SO 4°, and metal oxide magnetic powders such as iron, cobalt, nickel, and alloys thereof.

In the present invention, in addition to the above-mentioned binder and basic components of magnetic powder as components of the magnetic paint, a solvent and a dispersant are also included.

Various additives added to conventional magnetic coatings, such as lubricants, abrasives, and antistatic agents, may also be included.

The magnetic paint prepared with the required ingredients using a dispersion machine such as a sand mill is coated with a direct gravure roll, reverse roll, etc. on the conductive layer E-, which is a thin metal film previously provided on one side of a polyester film, and subjected to treatments such as magnetic field orientation. After that, the magnetic coating film is dried and then calendered using roll pressure bonding.

Hereinafter, the present invention will be explained using experimental examples.

Vacuum degree I x 10'-5 torr, oxygen temperature O,
Metal thin films of Cr having various thicknesses and surface resistances were vacuum-deposited under conditions of 1 to 21/min.

Cobalt-containing 7-Fe2O5'i 100 parts, MAG
10 parts of H (trade name: Vinyl chloride-vinyl acetate-vinyl alcohol copolymer manufactured by U, T, C, USA) i, Niraporan 2304 (trade name: polyurethane manufactured by Nippon Polyurethane)
10 parts of cyclohexanone-methylisobutylketone mixed solvent (mixing ratio 1:1) i200 parts, Vul.
A magnetic paint was prepared by mixing and dispersing a paint component consisting of 5 parts of canXC-72R (carbon black manufactured by Cabot Rei Co., Ltd.) in a sand mill or the like. This magnetic paint was coated on metal thin films of various thicknesses so that the dry film thickness was 3 μm. Magnetic tapes were manufactured by applying the magnetic paint 11 times, aligning with a magnetic field, and drying.Comparative examples will now be shown.

Experiment I + 1lJ) The magnetic paint was tuned and bent under the same conditions as in the experimental example, except that the amount of carbon black added was increased to 2 parts, and the metal thin film was applied in the same way to the base film without any heat. Manufactured magnetic tape.

In addition, in the experimental examples and comparative examples, parts are all heavy hY.
means part.

Regarding the magnetic tapes obtained in the experimental examples and comparative examples described below, the surface electrical resistance of the tape (J I S Ci 6240
The results of measuring the residual magnetic flux density (Br), and squareness ratio are shown in the drawing. Note that the thickness of the metal thin film was read from an electron micrograph (cross section) F.

As shown in the figure, the magnetic recording medium manufactured by the method of the present invention has a conductive layer between the magnetic coating film and the base film, so the surface electrical resistance is small and the charging voltage is low.
It is clear that C has excellent rod performance in terms of magnetic properties, as the harmful effects of C are suppressed, and C reduces the sagging of carbon black.

Note that even if a ferromagnetic material such as N1 is used for the metal, the thickness of the metal N film is 0.1 μm or less, so the saturation magnetic flux is about 0.01 Maxel, and there is no magnetic influence on the magnetic coating. isn't it.

[Brief explanation of the drawing]

The figure is a characteristic diagram showing a comparison between each experimental example of the present invention and a comparative example.

Claims (2)

[Claims] (1) A thin metal film with a thickness of 0.01 to 0.1 μm is formed on one side of a non-magnetic plastic film base, and a magnetic coating film made of magnetic powder and a required binder is formed on this thin metal film. A magnetic recording medium characterized by: (2) The surface specific resistance value of the metal special film is 1 to 106Ω
The magnetic recording medium according to claim 1 which is /Q.