JPH0619833B2 - Magnetic recording medium - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording medium such as a magnetic tape or a magnetic disk, and more particularly to a magnetic recording medium most suitable for a rotary head type video tape recorder.

Structure of conventional example and its problems Iron, cobalt, nickel or alloys containing them as a main component are formed by vacuum deposition, sputtering, ion plating, or other vacuum film forming methods such as polyester film, polyimide film, or other polymeric film or non-polymer film. The ferromagnetic metal thin film type magnetic recording medium formed on the substrate made of a magnetic metal thin plate can dramatically improve the recording density as compared with the conventional coating type magnetic recording medium. In order to increase the density, it is necessary to flatten the surface of the magnetic recording medium as much as possible to reduce the spacing cross between the magnetic head and the magnetic recording medium as much as possible. However, if the surface is excessively flattened, the head touch and running performance will be hindered, and the reproduction life of the video signal may be extremely short in the still mode during reproduction. These problems have been solved by providing a surface coating layer made of various organic lubricants and resins at the same time as finely roughening the surface. As such surface coating materials, various fatty acids, fatty acid esters, fatty acid amides, lubricants such as silicone oil and fluorine oil, and resins such as polyamide resin and epoxy resin have been used alone or in various composite forms. . But,
Looking at the still reproduction life, these products usually have a life of 30 minutes or longer at room temperature and normal humidity, but when the humidity becomes 20% RH or less, further 15% RH or less, the life becomes 30 minutes or less. As a result of the study by the present inventors, it became clear that many white spots running laterally appeared in the reproduced image even if the whiteness decreased or not decreased.

An object of the present invention is to solve the above problems and to provide a thin film type magnetic recording medium which can obtain good image quality during still reproduction under low humidity and has a long reproduction life.

Structure of the Invention The present invention comprises a ferromagnetic metal thin film containing oxygen having a carbon-carbon double bond and having a branched unsaturated perfluoroalkyl group branched by at least one of the carbons. The present invention relates to a magnetic recording medium characterized in that a thin layer containing a low molecular weight fluorine compound is formed, which is a ferromagnetic metal due to the strong sliding action of the branched unsaturated perfluoroalkyl group in low humidity. By preventing the magnetic head from adhering, it is possible to stabilize the still reproduction under low humidity and improve its life. The branched unsaturated perfluoroalkyl group is an oligomer (dimer, trimer, etc.) obtained by anionic polymerization of tetrafluoroethylene or hexafluoropropylene in a polar solvent in the presence of a base or fluoride ion. A perfluoroalkyl group having a carbon-carbon double bond derived from) and branched at at least one of the carbons,
As a typical example, Etc., C ₆ F ₁₁ -, or, C ₉ F ₁₇ - some are represented by, in particular a part of the fluorine-containing compound having a latter group, marketed by Corporation Neos. They are,
Compared with general-purpose perfluoroalkyl groups obtained by telomerization method, electrolytic fluorination method, etc., they are greatly different in that they are branched and have an unsaturated carbon bond. Is considered to have contributed significantly to the stabilization of still reproduction characteristics at low humidity.

Description of Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a diagram showing the basic structure of a magnetic recording medium in an embodiment of the present invention. In the figure, 1 is a substrate, 2 is a ferromagnetic metal thin film, and 3 is a surface coating layer. The surface coating layer 3 is composed of a thin film containing a fluorine-containing low molecular weight compound having a branched unsaturated perfluoroalkyl group.

Examples of the fluorine-containing low molecular weight compound having a branched unsaturated perfluoroalkyl group used in the present invention include (1) perfluoroalkylcarboxylic acid C ₉ F ₁₇ OCH ₂ CH ₂ OCOCH ₂ CH ₂ COOH (2) Perfluoroalkyl alcohol C ₉ F ₁₇ OCH ₂ CH ₂ OCH ₂ CH ₂ OH (3) Perfluoroalkyl phosphoric acid or salt thereof (4) Perproloalkylamide (5) Perfluoroalkyl ether C ₉ F ₁₇ OCH ₂ CH ₂ OCH ₂ CH ₂ OC ₉ F ₁₇ (6) Perfluoroalkyl ester (7) Perfluoroalkyl mercaptan It is _{C 9 F 17 OCH 2 CH 2} OCH 2 CH 2 SH , or the like. The fluorine-containing low molecular weight compound used in the present invention has at least one branched unsaturated perfluoroalkyl group, and the ratio of the molecular weight of the perfluoroalkyl group to the total molecular weight is 50% or more. What is best is. If this ratio is 50% or less, it becomes difficult to obtain the effects of the present invention. Wherein during the fluorine-containing compound, saturated perfluoroalkyl group obtained by other method (for _{example, C 9 F 19 -, C} 8 F 17 - , etc.) or an aliphatic alkyl group (e.g. C ₁₂ H ₂₅ -, _{C 18 H 37 -, C 18} H 35 - it is also possible to include and the like) and the like.

On the ferromagnetic metal thin film, the fluorine-containing low molecular weight compound is 0.1 to 500 mg, preferably 0.5 to ² per 1 m ² of surface.
Independently in the proportion of 00mg, or other lubricants, rust inhibitors,
It is preferable to allow it to exist in a thin layer as a composite with a resin or the like. Further, as a method of making it exist, in addition to the method of directly coating or vapor depositing on the ferromagnetic metal thin film, it is applied or vapor deposited on the back surface of the magnetic recording medium to make it ferromagnetic when laminating (winding) the magnetic recording medium. A method of transferring the surface of the metal thin film is also possible.

As the ferromagnetic metal thin film, for example, a metal thin film mainly composed of Co, Ni, Fe or the like formed by oblique deposition or vertical deposition, or a metal thin film mainly composed of an alloy thereof (for example,
(CoNi, CoCr, etc.), which contains oxygen obtained when the atmosphere during film formation is such that oxygen gas is dominant. The content of oxygen is at least 3% or more, preferably 5% by atomic ratio relative to the ferromagnetic metal.
% Or more is suitable. If it is 3% or less, it becomes difficult to obtain the effect of the present invention.

As a substrate on which the ferromagnetic metal thin film is to be formed, one having macroscopically good surface smoothness and having fine projections is suitable. For example, a substrate having a height of 50 to 600 Å
Polyester films having an average of 1 × 10 ⁴ to 10 ⁸ wavy or mountain-shaped protrusions per mm ² are particularly preferable.

Example A wavy projection (height 100 Å density 1 x 1 × was obtained by coating and curing a modified silicone emulsion liquid containing a thickener on the surface of a polyester film containing almost no fine particles caused by a polymerization catalyst residue during the film-forming process. 10 ⁶ pieces) on top of which was formed by continuous vacuum oblique vapor deposition.
A Ni ferromagnetic metal thin film (Ni = 20%, film thickness 1000Å) was formed in the presence of a slight amount of oxygen. The oxygen content in the film was 5% in terms of atomic number ratio. This sample is designated as A.

There are several granular projections (average height 70 Å average diameter 1 μm) per 100 μm ^{2 on the} surface due to the silica fine particles added in the polyester film, and relatively large projections due to fine particles due to polymerization catalyst residue are present as much as possible. Diameter 1 on the surface of the reduced polyester film
Under the same conditions as above, a CONi film (Ni) was formed on a substrate on which 1 × 10 ⁷ abrupt mountain-shaped protrusions having 50 Å silica colloidal particles as a nucleus and an ultraviolet curable epoxy resin as a binder were formed.
= 20%, film thickness 1000Å, oxygen content 7%) is defined as B. In addition, as a comparative example, C in which B was not introduced with oxygen during vapor deposition (B in which only the oxygen content was 2% or less) is designated as C. A solution of various fluorine-containing compounds prepared in advance is applied on these vapor-deposited films to form a thin layer, and then a magnetic tape cut into a predetermined width is made, and these are made into a prototype video deck at 20 ° C and 15% RH. Then, the still reproduction characteristics were measured and the time at which a white spot running laterally in the reproduced image began to appear (white spot occurrence time) and the time at which the reproduced image began to be completely disturbed (lifetime) were obtained. The results are summarized in the following table. As comparative examples, saturated perfluoroalkyl group-containing fluorine-containing compounds, (10), (11), (12), higher fatty acids and their derivatives,
...... (13), those with low oxygen content in the magnetic film ...... (7) are added.

EFFECTS OF THE INVENTION As is clear from Table 1, the magnetic recording medium of the present invention has a very high practical value because good image quality is obtained during still reproduction under low humidity and the life is stable for a long time. It is a thing.

[Brief description of drawings]

The drawing is a cross-sectional view of an embodiment of the magnetic recording medium of the present invention. 1 ... Substrate, 2 ... Ferromagnetic metal thin film, 3 ... Surface coating layer.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toshiaki Kunieda 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Yasuhiro Nishizawa, 1006 Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd. 72) Inventor Shogo Hogo, 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (56) Reference JP-A-60-231909 (JP, A)

Claims (1)

[Claims] 1. A fluorine-containing fluorine-containing oxygen-containing ferromagnetic metal thin film having a carbon-carbon double bond and having a branched unsaturated perfluoroalkyl group branched by at least one of the carbons. A magnetic recording medium characterized in that a thin layer containing a low molecular weight compound is formed.