JPH071540B2 - 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 particularly to a magnetic recording medium most suitable for a rotary head type video tape recorder.

Conventional technology Cobalt, nickel, iron, or alloys containing them as the main component are made of polymer film such as polyester film or polyimide film by vacuum film forming method such as vacuum deposition, sputtering, ion plating, or non-magnetic metal thin plate. The ferromagnetic metal thin film magnetic recording medium formed on the substrate can dramatically improve the recording density as compared with the conventional coating type magnetic recording medium. It is necessary to flatten the surface of the magnetic recording medium as much 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 excessively flattened, head touch and runnability will be impaired, so it is necessary to solve this by finely roughening the surface and at the same time providing a surface coating containing various organic lubricants.
Conventionally, as such an organic lubricant, various fatty acids, fatty acid esters, fatty acid amides, silicone oils, fluorine oils, etc. have been used alone or in the form of various composites.

Problems to be Solved by the Invention A medium using the above various organic lubricants usually has a still life of 30 at room temperature to high temperature (10 to 30 ° C.).
As a result of the study conducted by the present inventors, it has been revealed that although it has a life of not less than a minute, the life decreases to 30 minutes or less, and sometimes to a few minutes or less when the temperature becomes 5 ° C. or less.

Means for Solving the Problems The present invention relates to a magnetic recording medium characterized in that a thin film containing a specific fluorine-containing organic phosphorus compound is formed on a ferromagnetic metal thin film containing oxygen. The thin layer of phosphorus compound and the oxide layer on the surface of the ferromagnetic layer solve the above problems. The organic phosphorus compound is represented by the following general formula (I).

General formula (I): [ _One or _{two of} R ₁ , R ₂ and R ₃ has 3 or more carbon atoms 20
The following fluoroalkyl derivative residues, and R ₁ ,
Other than the above R ₂ and R ₃ are aliphatic hydrocarbon groups having 8 to 30 carbon atoms.

k, l, m and n each represent an integer of 0 or 1,
At least one of k, l, m and n is 1.

W, X, Y and Z each represent a sulfur or oxygen atom, and at least one or more of those whose coefficients l, m, n and k are 1 are sulfur atoms. ] With the above-mentioned structure, the stable lubricity of the fluoroalkyl group in the organophosphorus compound and the strong reaction force of the phosphorus atom / sulfur atom on the surface of the ferromagnetic layer allow a synergistic effect at low temperatures. The still regeneration life is improved, and the effect is remarkable because the organic phosphorus compound used contains an aliphatic hydrocarbon group.

Embodiment FIG. 1 is an enlarged sectional view 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. Surface coating layer 3
Is formed of a thin layer containing the above specific organic phosphorus compound.

The specific organophosphorus compound used in the present invention is, for example, C _n F _{2n + 1} (CH ₂ ) _m as a fluoroalkyl derivative residue in the R ₁ , R ₂ and R ₃ components in the above general formula. − HCF ₂ (CF ₂ ) _2n (CH ₂ ) _m − C _n F _2n-1 O (CH ₂ ) _m − (However, n = 3 to 20, m = 1 to 10, R is H, CH ₃ or C ₂ H ₅ ) Further, as an aliphatic hydrocarbon group, for example, C _n H _{2n + 1} − C _n H _2n-1 − (However, n = 8 to 30).

As the fluoroalkyl group, a linear or branched perfluoroalkyl group having 3 or more carbon atoms, more preferably 5 or more carbon atoms,
Alternatively, a straight-chain fluoroalkyl group having one hydrogen atom at a terminal carbon atom having 3 or more carbon atoms, more preferably 5 or more carbon atoms (for example, HCF ₂ CF ₂ CF ₂ CF ₂ CF ₂ —) is suitable and has 2 carbon atoms.
In the following cases, the still life becomes short. The number of carbons is
When it is 21 or more, there is no solvent that can be diluted and the melting point rises to approach the decomposition temperature, making it difficult to use as a thin layer. As the aliphatic hydrocarbon residue, a linear or branched alkyl group having 8 or more carbon atoms, and more preferably 10 or more carbon atoms is suitable.

If the number of carbon atoms is 31 or more, there is no solvent that can be diluted, and the melting point also rises to approach the decomposition temperature, making it difficult to use as a thin layer. One or two of R ₁ , R ₂ and R ₃ in the above general formula must be the above fluoroalkyl derivative residue. When the fluoroalkyl derivative residue is zero, the still life becomes extremely long. descend. Also, R ₁ ,
Other than the above R ₂ and R ₃ , it is necessary that they are aliphatic hydrocarbon groups.

On the ferromagnetic metal thin film, the above-mentioned organic phosphorus compound is 0.1 to 500 mg, more preferably 0.5 to 200 mg per 1 m ² of the surface, individually or as a composite with another lubricant, rust preventive, resin or the like. It is better to make them exist in layers. Further, as a method of making them exist, other than the method of directly coating or vapor depositing on the surface of the ferromagnetic metal thin film, coating or vapor depositing on the surface of the magnetic recording medium is carried out, and when the magnetic recording medium is laminated (wound), it is ferromagnetic. A method of transferring to 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 an oblique deposition method or a vertical deposition method, or a metal thin film mainly composed of an alloy thereof (eg CoNi, C
(eg, oCr), which contains oxygen obtained when the atmosphere gas during film formation is an atmosphere in which oxygen gas is dominant. The oxygen content is at least 3% or more, preferably 5% or more, in terms of atomic number ratio to the ferromagnetic metal. If it is 3% or less, it is difficult to obtain the still life improvement effect at low temperatures.

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

In addition, a wavy pattern (height 100 Å density was obtained by coating and curing a modified silicone emulsion liquid containing a thickening agent on the surface of a polyester film containing almost no fine particles caused by residual polymerization catalyst during the stretching process. 1 x 10
CoNi ferromagnetic metal thin film (Ni = 20%, film thickness 1000 Å) was formed on top of the thin film ( ⁶ pieces) by continuous vacuum oblique deposition method in the presence of a trace 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 70Å, average diameter 1 μm) per 100 μm ^{2 on the} surface due to silica fine particles added in the polyester film, and relatively large projections due to the fine particles due to the residual polymerization catalyst. Diameter of 150 Å on the surface of polyester film
CoNi film (Ni = 20%, film thickness) under the same conditions as above on a substrate on which 1 × 10 ⁷ steep mountain-shaped protrusions with the silica colloid particles as the core and the ultraviolet curing epoxy resin as the binder were formed. Let B be 1000Å and oxygen content 7%). 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. Various organic compound solutions that were synthesized and prototyped were applied on these vapor-deposited films in advance to form a thin layer, which was then cut into a predetermined width to make a magnetic tape, which was then mounted on a prototype video deck at -5 ° C to be used as a still. The reproduction characteristics were measured. The still reproduction life was defined as the time until the output dropped 10 dB from the initial value. The results are summarized in the following table.

As a comparative example, a magnetic film having a low oxygen content ... Comparative Example 9 Fluoroalkyl group-free ... Comparative Examples 10 and 11 are added.

EFFECTS OF THE INVENTION As is clear from the above results, the magnetic recording medium of the present invention has a long still reproduction life at low temperature and is stable, and thus has an extremely high industrial value.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an enlarged sectional view of a magnetic recording medium according to an embodiment of the present invention. 1 ... Substrate, 2 ... Ferromagnetic metal thin film, 3 ... Surface coating layer.

Front page continuation (72) Inventor Nobuo Nakamura 1006, Kadoma, Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Inventor, Susumu Enomoto 1006, Kadoma, Kadoma, Osaka (56) Reference Document JP-A-61-104320 (JP, A)

Claims (1)

[Claims] 1. A magnetic recording medium characterized in that a thin film containing a fluorine-containing organic phosphorus compound represented by the following general formula (1) is formed on a ferromagnetic metal thin film containing oxygen. General formula (1): [ _One or _{two of} R ₁ , R ₂ and R ₃ has 3 or more carbon atoms 20
The following fluoroalkyl derivative residues, and R ₁ ,
Other than the above R ₂ and R ₃ are aliphatic hydrocarbon groups having 8 to 30 carbon atoms. k, l, m and n each represent an integer of 0 or 1,
At least one of k, l, m and n is 1. W, X, Y and Z each represent a sulfur or oxygen atom, and at least one or more of those whose coefficients l, m, n and k are 1 are sulfur atoms. ]