JPS61107529A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To provide a long and stable still reproduction life at a low temp. by forming a thin layer contg. an org. compd. having respectively >=1 fluoroalkyl group, aliphat. alkyl group and carboxyl group on a thin ferromagnetic metallic film contg. oxygen. CONSTITUTION:This magnetic recording medium is constituted by forming the thin layer contg. the org. compd. having respectively >=1 fluoroalkyl group of >=3C, aliphat. alkyl group of >=8C and carboxyl group 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 powerful reactive force of the carboxyl group on the oxide layer of 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 most 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 thin film magnetic recording medium formed on a substrate made of a magnetic thin plate or the like can dramatically improve recording density compared to conventional coated 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 too flattened, head touch and running properties will be affected, so it is necessary to solve this problem by making the surface finely rough and at the same time providing a surface coating containing various organic lubricants. 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 combinations. However, when looking at the still playback life, these products usually have a lifespan of 30 minutes or more at room temperature to high temperatures (10 to 30°C), but when the temperature drops below 5°C, the lifespan decreases to 30 minutes. As a result of the studies conducted by the present inventors, it has become clear that the time decreases to several minutes or less in some cases.

OBJECTS OF THE INVENTION The present invention solves the above problems and provides a thin-film 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 having one or more each of a 70-roalkyl group having 3 or more carbon atoms, an aliphatic alkyl group having 8 or more carbon atoms, and a carboxyl group at the molecular end of the molecule. This relates to a magnetic recording medium formed on a magnetic metal thin film, which is characterized by the stable lubricity of fluoroalkyl groups and aliphatic alkyl groups and the effect of carboxyl groups on the oxide layer on the surface of the ferromagnetic metal thin film. The synergistic effect with the strong reaction force improves the life of still playback at low temperatures.

Description of Embodiment 3 An embodiment of the present invention will be described below with reference to the drawings.

The figure is a diagram showing the basic configuration 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 layer containing an organic compound having at least one 70-roalkyl group having 3 or more carbon atoms, an aliphatic alkyl group having 8 or more carbon atoms, and a carboxyl group at the molecular terminal.

Examples of the organic compound having a fluoroalkyl group (denoted as Rf), an aliphatic alkyl group (denoted as R), and a carboxyl group used in the present invention include polyhydric alcohol ester derivatives.

HH R-CH(CH2)8C○○H (Rf Unsaturated fatty acid derivative.

Examples include alkylamine derivatives and alkylsuccinic acid derivatives. The 70-roalkyl 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 5 or more carbon atoms (for example, HCF2CF2CF2CF2CF2-
) is suitable, and if the number of carbon atoms is 2 or less, the steal life will be shortened.

As the aliphatic alkyl group, a linear 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 above fluoroalkyl group, aliphatic alkyl group, and carboxyl group as a terminal group in the same molecule, and any one of them, However, if organic compounds having two types of terminal groups are mixed and in a mixed state, the above 3.
Even if the terminal groups of various species are arranged, 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, hydrocarbon groups having 7 or less carbon atoms such as CH3-, C2H5-, HCF2-).

A fluoroalkyl group having 2 or less carbon atoms, such as C2F5-.

) may also exist.

The molecular weight of the organic compound used in the present invention is 3.
,000 or less, more preferably 0,000 or less. If the molecular weight is 3,000 or more, the output during stilling becomes unstable.

The ratio of each terminal group in the organic compound is 10 to 10 fluoroalkyl groups having 3 or more carbon atoms in terms of molecular weight ratio.
80, 10 to 80 aliphatic alkyl groups having 8 or more carbon atoms
%, and the carboxyl group is suitably 3 to 20%. 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 added at a concentration of 0.1 to soo rtty per surface, more preferably O
, Sm2O3, alone, or in a thin layer as a composite with other lubricants, rust preventives, resins, etc. Also, as a way to make it exist,
In addition to the method of directly coating or vapor depositing on the surface of the ferromagnetic metal thin film, it is also possible to coat or vapor deposit it on the back side of the magnetic recording medium and then transfer it to the surface of the ferromagnetic metal thin film when stacking (winding) the magnetic recording medium. It is.

The ferromagnetic metal thin film may be, for example, a metal thin film mainly made of Co, Ni, Fe, etc. formed by oblique evaporation or vertical evaporation, or a metal thin film mainly made of alloys thereof (e.g. CoNi, CoCr, etc.). A suitable material is one containing oxygen, which can be obtained when the atmosphere during film formation is dominated by oxygen gas. The oxygen content is suitably at least 3% or more, preferably 5% or more in terms of atomic ratio to one ferromagnetic metal. If it is less than 3 inches, it is difficult to obtain the effect of improving the still life at low temperatures.

As a substrate on which a 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 x 10 to 10 wave-like or mountain-like protrusions are particularly preferred.

Example Wave-like protrusions (height: 100, density: 1 x 106 pieces) was formed, and then a pcoNi ferromagnetic metal thin film (Ni = 20 cm, film thickness 100 cm) was formed by continuous vacuum diagonal evaporation.
0) was formed in the presence of trace amounts 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 (average height 70, average diameter 1 μm) with a gentle slope due to silica particles added to the polyester film per 10 μm2 of the surface, and these are caused by polymerization catalyst residue. A substrate on which 1 x 10 steep mountain-like protrusions are formed using ultraviolet curing epoxy resin as a core and a core of silica colloid particles with a diameter of 150 mm on the surface of a polyester film that minimizes relatively large protrusions caused by fine particles. A Co Ni film (Ni=20%, film thickness 1000, oxygen content 7%) was formed under the same conditions as above. Further, as a comparative example, C is a sample in which no oxygen was introduced during vapor deposition in B (a sample in which only the oxygen content in B was 2% or more). Various organic compound solutions pre-synthesized and prototyped were coated onto these vapor-deposited films to form a thin layer, and then cut into predetermined widths to make magnetic tapes, which were hung on a prototype video deck at -6°C. The still playback characteristics were measured. The still playback life was defined as the time until the output decreased by 10 dB from the initial value. The results are summarized in Table 1. As a comparative example, one without 70-roalkyl group...
...(1S), without aliphatic alkyl group...
・(12), without carboxyl group...
・(14) Magnetic film with low oxygen content...
) 1st prize is added.

Effects of the Margin 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.

[Brief explanation of the drawing]

The drawing is a sectional view of one embodiment of the magnetic recording medium of the present invention. 1...Substrate, 2...Ferromagnetic metal thin film,
3...Surface coating layer. Name of agent: Patent attorney Toshio Nakao and 1 other person-1
to 7

Claims (1)

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