JPS61107527A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To provide a magnetic recording medium having a long and stable still reproduction life at a low temp. by forming a thin layer contg. a specific org. compd. on a thin ferromagnetic metallic film contg. oxygen. CONSTITUTION:The thin layer contg. the org. compd. having respectively one fluoroalkyl group of >=3C, aliphat. alkyl group of >=8C and mercapto group at the molecular terminal is formed on the thin ferromagnetic metallic film contg. oxygen. The still reproduction life at the low temp. is improved by the synergistic effect of the stable lubricating effect possessed by the fluoroalkyl group and aliphat. alkyl group and the strong reactive power of the mercapto group to the oxide layer on the surface of the thin ferromagnetic metallic film.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is suitable for magnetic recording media such as magnetic tapes and magnetic disks, and particularly relates to a magnetic recording medium suitable for rotary head type video tape recorders.

Structures of conventional examples and their problems Iron, cobalt, nickel, or alloys containing these as main components are used in vacuum film forming methods such as vacuum evaporation, sputtering, and ion blasting to produce polymer films such as polyester films, polyimide films, and A ferromagnetic metal drop type magnetic recording medium formed on a substrate made of a magnetic thin plate or the like can dramatically improve recording density compared to conventional coating type magnetic recording media. In order to increase the density, it is necessary to make the surface of the magnetic recording medium as flat as possible to reduce the spacing loss between the magnetic head and the magnetic recording medium as much as possible.

However, if the surface is made too flat, it will interfere with the head touch and running performance, so it is necessary to finely roughen the surface and at the same time provide a surface coating containing various organic lubricants.
need to be resolved. Conventionally, as such organic lubricants, various fatty acids, fatty acid esters, fatty acid amides, silicone oils, fluorine oils, etc. have been used singly or in various composite forms. However, when looking at the still playback life, those of Ton et al.
), the lifespan is usually 30 minutes or more, but as a result of the inventors' studies, it has been found that when the temperature drops below 5C, the lifespan decreases to less than 30 minutes, and sometimes less than a few minutes. .

OBJECTS OF THE INVENTION The present invention solves the above problems and provides a magnetic recording medium that has a long still playback life at low temperatures.

Structure of the Invention The present invention provides a thin layer containing an organic compound each having at least one fluoroalkyl group having 3 or more carbon atoms, an aliphatic alkyl group having 8 or more carbon atoms, and 1 or more mercapto groups at the molecular terminal, by removing oxygen. The present invention relates to a magnetic recording medium formed on a ferromagnetic metal thin film containing a stable lubricating effect of fluoroalkyl groups and aliphatic alkyl groups and oxidation of the surface of the ferromagnetic metal thin film of mercapto groups. The synergistic effect with the strong reaction force to the layer improves the life of still playback at low temperatures.

Description of Examples Fluoroalkyl group (denoted as Rf) used in the present invention
vinegar. ), an aliphatic alkyl group (denoted as R), K, and a mercapto group, such as polyhydric alcohol ester derivatives and mercapto fatty acid derivatives.

Thiocarboxylic acid (thiodingic acid, α-methylthiomalic acid, thiocoheriic acid, thioheptatalic acid, etc.) derivatives.

OOR 5-CH CM2C0OCH2CH2R.

(+; 12 Shiri (JI: M 2CM 2 N (J
S CJ kL fR ■ HCOOR CH2Co0CH2CH2Rf Mercaptoaminocarboxylic acid (cystine, etc.) derivative, -R HSCH2-CH-Co○CH2CH2Rf.

etc. The fluoroalkyl group has 3 or more carbon atoms,
More preferably, a linear or branched perfluoroalkyl group having 5 or more carbon atoms, or a linear fluoroalkyl group having one hydrogen atom at the terminal carbon having 3 or more carbon atoms, and more preferably 6 or more carbon atoms (for example, HCF2CF2CF2CF2CF2-
) is suitable, and if the number of carbon atoms is 2 or less, the still life will be shortened.

As the aliphatic alkyl group, a straight chain or branched alkyl group having 8 or more carbon atoms, more preferably 10 or more carbon atoms is suitable, and even if the carbon number is 7 or less, the still life is reduced. The organic compound used in the present invention must have at least one of each of the fluoroalkyl group, aliphatic alkyl group, and mercapto group as a terminal group in the same molecule; Alternatively, even if organic compounds having two types of terminal groups are mixed and the three types of terminal groups described above are arranged in a mixed state, it is difficult to obtain the same effect as the present invention. A plurality of each of the above groups can be present in the same molecule, and terminal groups other than the above (for example, CH3-, C2H6-).

A hydrocarbon group having 7 or less carbon atoms such as HCF2-.

A fluoroalkyl group having 2 or less carbon atoms, such as 02F, -, etc.

etc.) can also exist.

The molecular weight of the organic compound used in the present invention is 3.
,000 or less, more preferably 2,000 or less. If the molecular weight is 3,000 or more, the output during stilling becomes unstable.

As for the ratio of each terminal group in the organic compound, the molecular weight ratio is 10 to 5 fluoroalkyl groups having 5 or more carbon atoms.
80%, aliphatic alkyl group having 8 or more carbon atoms is 10-8o
%, and 2 to 16 mercapto groups are suitable. Outside this range, it is difficult to obtain the effect of improving the life of the still at low temperatures.

On the ferromagnetic metal thin film, the organic compound is applied to the surface 1rr.
? 0.1-60omg, more preferably 0.5
It is preferable to make it exist in a thin layer at a ratio of ~200 cm, either alone or as a composite with other agents, anti-chain agents, resins, etc. In addition, methods for making it exist include coating or vapor-depositing it directly on the surface of the ferromagnetic metal thin film, or coating or vapor-depositing it on the back side of the magnetic recording medium so that it is strong during stacking (winding) of the magnetic recording medium. A method of transferring it to the surface of a magnetic metal thin film is also possible.

As the ferromagnetic metal thin film, for example, C o , N i , Fe formed by oblique evaporation or vertical evaporation method is used.
A metal thin film mainly composed of alloys of these metals (e.g. CoNi, CoCr, etc.), which is obtained when the atmosphere during film formation is dominated by oxygen gas. It is appropriate to include. The oxygen content is suitably at least 3% or more, preferably 5% or more in terms of atomic ratio to the ferromagnetic metal. If it is less than 3%, it is difficult to obtain the effect of improving still life at low temperatures.

As the substrate on which the ferromagnetic metal thin film is to be formed, it is appropriate to use one that has good macroscopic surface smoothness and has minute protrusions.
- Polyester films having an average of 1×104 to 188 wavy or convex protrusions are particularly preferred.

(Example: In the process of forming a stretched film on the surface of a polyester film that contains almost no particulates caused by polymerization catalyst residue.
f) CoNi strength was formed by continuous vacuum oblique vapor deposition on the wavy protrusions (height: 10 OA density: 1 x 106 pieces) obtained by coating and curing a modified silicone emulsion containing a thickener. Magnetic metal thin film (N i =
20%, film thickness 100%) was formed in the presence of a trace amount of oxygen. The oxygen content in the film was 5% in terms of atomic ratio. This sample is designated as A.

There are several granular protrusions with a gentle slope (average height: 70 people, average diameter: 1 μm) per 100 μm' of surface due to silica fine particles added to the polyester film, and relatively large protrusions due to fine particles caused by polymerization catalyst residue. The surface of the polyester film has a diameter of 1
A Co Ni film (N i = 20 cm) was formed under the same conditions as above on a substrate on which 1 x 10 7 steep mountain-like protrusions were formed using silica colloid particles as cores and UV-curable epoxy resin as a binder. , film thickness 1000, oxygen content 7%
) is formed as B. In addition, as a comparative example, in B, no oxygen was introduced during vapor deposition (B
C) in which only the oxygen content is 2% or less. Various organic compound solutions synthesized and prototyped in advance were coated on these vapor-deposited films, and then cut into predetermined widths to make magnetic tapes.These tapes were hung on a prototype video deck in -5C to test the stealth playback characteristics. It was measured. The still playback life is
The time required for the output to decrease by 10 dB from the initial value was taken as the time.

The results are summarized in Table 1. In addition, as a comparative example, one without fluoroalkyl group...(9).

Those without an aliphatic alkyl group (10), those without a mercapto group (11), those with a low oxygen content in the p magnetic film (7), etc. are added.

Effects of the Invention As is clear from the above results, the magnetic recording medium of the present invention has a long and stable still playback life at low temperatures, and therefore has extremely high practical value.

Claims (1)

[Claims] Fluoroalkyl group with 3 or more carbon atoms and 8 carbon atoms at the end of the molecule
1 each of the above aliphatic alkyl groups and mercapto groups
1. A magnetic recording medium characterized in that a thin layer containing an organic compound having at least one oxygen is formed on a ferromagnetic metal thin film containing one oxygen.