JPS6113437A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a thin ferromagnetic metallic film type magnetic recording medium which is free from curling by coating an emulsion having a specific glass transition point or below on a non-magnetic substrate and forming a thin ferromagnetic metallic film on the continuous film. CONSTITUTION:The uniform continuous film can be formed by coating the emulsion having <=30 deg.C glass transition point on the non-magnetic subsrate. Since the continuous film is softer than the magnetic layer and non-magnetic substrate, said film disperses the stress concentration and relieves the stress to be generated between the magnetic layer and the non-magnetic substrate. The magnetic recording medium which is free from curling is thus obtd. For example, a polyvinyl acetate emulsion, etc. are used for the emulsion. The non-magnetic substrate is exemplified by plastics including polyester such as polyethylene terephthalate and polyamide imide. The thin ferromagnetic metallic film material is exemplified by metals or alloys such as Fe, Co and Ni or the metals or alloys incorporated therein with metals such as Cr and Al. The means for depositing the thin ferromagnetic metallic film material is exemplified by a vacuum deposition method, ion plating method, sputtering method, etc.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to magnetic recording of a so-called ferromagnetic metal thin film type in which a ferromagnetic metal thin film is formed on a nonmagnetic support by vapor deposition, ion blating, sputtering, etc. It's about the medium.

[Background technology and its problems]

Conventionally, as a magnetic recording medium, r-
γ-Fe20B containing FezOa, Co, Fe
FeaO* containing 3O4, Co, r-Fe20
a and F e s O4 hertolide compounds, CO-containing bertolide compounds, oxide magnetic powders such as Cr0z, or Fe.

Coating type magnetic recording in which a powder magnetic material such as an alloy magnetic powder mainly composed of Co, Ni, etc. is dispersed in an organic binder such as vinyl chloride-vinyl acetate copolymer, polyester resin, polyurethane resin, etc., and then applied and dried. media have been widely used.

In recent years, with the increasing demand for high-density magnetic recording, metal thin films made of ferromagnetic metals have been deposited directly onto non-magnetic supports using vacuum evaporation, sputter linking, ion platelic, and plating techniques. The ferromagnetic thin film magnetic recording media created by this method are attracting attention. This ferromagnetic metal thin film magnetic recording medium not only has a large coercive force Hc and a large residual magnetic flux density Br.

Because it is possible to make the thickness of the magnetic layer extremely thin,
It has many advantages in magnetic properties, such as extremely small thickness loss during recording demagnetization and reproduction, and the ability to increase the packing density of magnetic material because there is no need to mix a non-magnetic organic binder into the magnetic layer. It has the following advantages.

However, in this type of magnetic recording medium, since a vacuum evaporation method or the like is used as a means of forming the ferromagnetic metal thin film, the base film, which is a non-magnetic support, is susceptible to thermal damage. When the evaporated metal atoms recrystallize on top to form a thin film, they shrink and generate internal stress, which causes the ferromagnetic metal thin film to curl into a concave shape. When this kind of curl occurs, the contact between the magnetic recording medium and the magnetic head becomes poor, and
The playback output decreases, causing scratches and irregular winding.

Therefore, various methods have been proposed to eliminate the above-mentioned curls.

For example, after a magnetic thin film has been deposited, stress may be applied to the magnetic thin film to cause a type of crack in the magnetic thin film, thereby relaxing the strain stress.
-83706, JP-A-53-104204, etc. Further, it is disclosed in Japanese Patent Application Laid-Open No. 16032/1983 that stress is relaxed by subjecting the substrate to a heat treatment to shrink the substrate side after the magnetic thin film is deposited. Furthermore, stress relaxation can be achieved by providing a back coat layer on the back side of the magnetic recording medium, that is, on the side opposite to the magnetic layer, as disclosed in JP-A-56-11622 and JP-A-56-1693.
It is disclosed in Publication No. 9 etc.

However, none of these methods can prevent curling during film formation and has many drawbacks in terms of productivity and other aspects.

Curling during film formation is also an extremely serious problem even when using other deposition methods other than vapor deposition, such as spackling and ion plating, and a sufficient preventive measure has not yet been realized.

[Purpose of the invention]

The present invention has been proposed in view of the above-mentioned conventional situation, and an object of the present invention is to provide a ferromagnetic metal thin film magnetic recording medium that is free from curl.

[Means for solving problems]

That is, in the present invention, the glass transition point is 3 on the nonmagnetic support.
Apply an emulsion below 0℃ to form a continuous film,
The present invention relates to a magnetic recording medium characterized in that a ferromagnetic metal thin film is formed on this continuous film.

By coating an emulsion with a glass transition point of 30° C. or lower on a non-magnetic support, a uniform continuous film can be formed, and the continuous film is softer than the magnetic layer and the non-magnetic support. Therefore, the stress concentration generated between the magnetic layer and the nonmagnetic support is dispersed and relaxed, so that a magnetic recording medium without curling can be obtained.

Further, as the thickness of the continuous film increases, the amount of curl decreases, but as the thickness of the continuous film increases, the surface smoothness deteriorates, and the electromagnetic conversion characteristics of the magnetic recording medium deteriorate. Therefore, it is desirable that the thickness of the continuous film is 1 μm or less.

Examples of the emulsion having a glass transition point of 30°C or lower include polyvinyl acetate emulsion, polyacrylic acid ester emulsion, polyester emulsion, polyurethane emulsion, styrene-butadiene copolymer emulsion, polyisoprene emulsion, acrylonitrile-butadiene copolymer emulsion, etc. can be mentioned.

Examples of nonmagnetic supports include polyesters such as polyethylene terephthalate, polyolefins such as polyethylene and polypropylene, cellulose derivatives such as cellulose triacetate, cellulose diacetate, and cellulose acetate butylene, polyvinyl chloride, polyvinylidene chloride, etc. Examples include plastics such as vinyl resin, polycarbonate, polyimide, and polyamideimide. The nonmagnetic support may be in any form such as a film, tape, sheet, disk, cart, or tram.・As the ferromagnetic metal thin film material, metals such as Fe, Co, Ni, Co-Ni alloy, Fe-Co alloy, Fe-N
i alloy, Fe-Co-Ni alloy, Fe-Co-B alloy,
C.

Examples include -Ni-re-B alloys and those containing metals such as Cr and A1.

Examples of the means for depositing the ferromagnetic metal thin film material include a vacuum evaporation method, an ionplatic method, and a sputtering method. The above vacuum evaporation method uses 101 to 10-8 Tor.
The ferromagnetic metal material is evaporated by resistance heating, high-frequency heating, electron beam heating, etc. in a vacuum of 100 nm, and the evaporated metal (ferromagnetic metal material) is deposited on a non-magnetic support, and is an oblique evaporation method. and vertical evaporation methods. The above-mentioned oblique vapor deposition method is a method in which the above-mentioned ferromagnetic metal material is obliquely vapor-deposited on a non-magnetic support in order to obtain a high coercive force,
It also includes those in which the above-mentioned vapor deposition is performed in an oxygen atmosphere in order to obtain higher coercive force. In the above-mentioned vertical deposition method, Bi is deposited on a non-magnetic support in advance in order to improve deposition efficiency and productivity and to obtain high coercive force.

A base metal layer of Sb, Pb, Sn, In, Cd, Ge, Si, T1, etc. is formed in advance, and the above-mentioned ferromagnetic metal material is vertically deposited on this base metal layer.

The above-mentioned ion blasting method is also a type of vacuum evaporation method, and D
C claw discharge and RF glow discharge are caused, and the ferromagnetic metal is evaporated during the discharge. The above sputtering method involves causing a claw discharge in an atmosphere mainly composed of argon gas at 10 to 10 Torr, and using the generated argon ions to knock out atoms on the target surface.
There are three-pole sputtering methods, high-frequency sputtering methods, and magnetron sputtering methods that utilize magnetron discharge.

Furthermore, in order to improve the running properties of the magnetic recording medium, it is also possible to form a lubricant layer on the surface of the ferromagnetic metal thin film described above.

As the lubricant, fatty acids, fatty acid esters, fatty acid amides, metal soaps, aliphatic alcohols, paraffins, silicones, fluorine surfactants, etc. can be used, and the amount of the lubricant applied is 1 to 1100 (1/m2). is preferable.

As the fatty acid, those having 12 or more carbon atoms such as lauric acid, myristic acid, palmitic acid, stearic acid, hehe/acid, oleic acid, linoleic acid, and lilunic acid can be used.

As the fatty acid ester, ethyl stearate, butyl stearate, amyl stearate, monocryceride stearate, monocryceride oleate, etc. can be used.

Examples of fatty acid amides include caproic acid amide, capric acid amide, lauric acid amide, palmitic acid amide, stearic acid amide, behenic acid amide, oleic acid amide,
linoleic acid amide, methylene bisstearic acid amide,
Ethylene bisstearamide, etc. can be used.

Examples of metal soaps include Zn and Pb such as lauric acid, myristic acid, balmitic acid, stearic acid, behenic acid, oleic acid, linoleic acid, and linuric acid.

Salts with Ni, Co, F'e;A#, Mg, Sr, Cu, etc., salts of sulfonic acids such as lauryl, balmityl, myristyl, stearyl, behenyl, oleyl, linole, rinne, etc. with the above metals, etc. can be used. .

As the aliphatic alcohol, heptyl alcohol, stearyl alcohol, etc. can be used.

As the halafine, saturated hydrocarbons such as n-nonadecane, n-tridecane, and 11-tocosan can be used.

Noenyl tk (:') Polysiloxanes subjected to 7411 layer exchange and those modified with fatty acids, fatty alcohols, fatty acid amides, etc. can be used.

As the fluorine-based surfactant, perfluoroalkylcarboxylic acid and perfluoroalkylsulfonic acid and Na,
Salts with Mg, Zn, Al, Fe, Co, Ni, etc., perfluoroalkyl phosphate esters, perfluoroalkyl betaines, perfluoroalkyltrimethylammonium salts,
Perfluoroethylene oxide, perfluoroalkyl aliphatic ester, etc. can be used.

〔Example〕

Although specific examples of the present invention will be described below, it goes without saying that the present invention is not limited to these examples.

Example 1 A polyhinyl acetate emulsion with a glass transition point of 29° C. diluted with a water-n-propyl alcohol mixture containing 60% by weight of n-propyl alcohol was applied onto a 12 μm thick polyethylene terephthalate film. A continuous film with a coating thickness of 100λ was formed.

Next, cobalt CO was obliquely evaporated onto the continuous film using a vacuum evaporation device at an incident angle of 50° to 9° to a film thickness of about 130°.
A sample tape was prepared by forming an OA ferromagnetic metal thin film.

Example 2 A polyacrylic acid ester emulsion having a glass transition point of 0°C diluted with a water-n-propyl alcohol mixture containing 60% by weight of n-propyl alcohol was applied onto a polyethylene terephthalate film with a thickness of 12 μm. A continuous film with a coating thickness of 100A was formed.

Next, a sample tape was prepared in the same manner as in Example 1.

Example 3 A polyester emulsion with a glass transition point of 120° C. diluted with a water-normal propyl alcohol mixture containing 60% by weight of normal propyl alcohol was applied onto a 12 μm thick polyethylene terephthalate film. A continuous film with a coating thickness of 1 ooi was formed.

Next, a sample tape was prepared in the same manner as in Example 1.

Comparative Example Copal L-C was deposited on a 12 μm thick polyethylene terephthalate film using a vacuum evaporation device.

was obliquely deposited at an incident angle of 500 to 90°, and the film thickness was approximately 1300.
A sample tape was created by forming a large ferromagnetic metal thin film.

The measurement results for the amount of curl of the sample tape obtained are shown in the following table. The improvement ability curl amount is determined by measuring the amount shown in FIG.
The case where it is curved to the side is indicated by a minus sign.

Table [Effects of the Invention] It is clear from the above-mentioned Examples and Comparative Examples that according to the present invention, a ferromagnetic metal thin film type magnetic recording medium with almost no curl can be obtained. ).

Brief Description of Surface 40 FIG. 1 is a schematic cross-sectional view showing a curled state of a ferromagnetic metal magnetic recording medium.

Claims (1)

[Claims] 1. A magnetic recording medium characterized in that an emulsion having a glass transition point of 30° C. or lower is coated on a non-magnetic support to form a continuous film, and a ferromagnetic metal thin film is formed on the continuous film.