JPH0766538B2 - Magnetic recording medium - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of use] The present invention is a so-called magnetic thin film formed on a non-magnetic support as a magnetic layer by a technique such as vacuum thin film forming technology such as vacuum deposition or sputtering. The present invention relates to a ferromagnetic metal thin film type magnetic recording medium.

[Outline of the Invention] The present invention provides a magnetic recording medium comprising a ferromagnetic metal thin film formed as a magnetic layer on a non-magnetic support, wherein the ferromagnetic metal thin film as the magnetic layer has a perfluoroalkylcarboxylic acid ester and a thiazole group. By applying a protective layer containing a compound as a main component, it is intended to improve the running property, wear resistance, durability and corrosion resistance.

[Conventional technology]

Conventionally, γ-on a non-magnetic support has been used as a magnetic recording medium.
Fe ₂ O _3, containing _{Co γ-Fe 2 O 3,} Fe 3 O 4, containing Co Fe ₃ O
₄ , γ-Fe ₂ O ₃ and Fe ₃ O ₄ Bertride Compounds, Co-containing Bertride Compounds, Oxide Ferromagnetic Powders such as CrO ₂ or Alloy Magnetic Properties Containing Fe, Co, Ni, etc. as Main Components A coating type magnetic recording medium prepared by coating and drying a magnetic coating material prepared by dispersing a powder magnetic material such as powder in an organic binder such as vinyl chloride-vinyl acetate copolymer, polyester resin, polyurethane resin, etc. Widely used.

On the other hand, with the increasing demand for high-density magnetic recording, a ferromagnetic metal material such as Co-Ni alloy is coated with polyester by plating or vacuum thin film forming technology (vacuum evaporation method, sputtering method, ion plating method, etc.). Directly deposited on a non-magnetic support such as a film or polyimide film,
A so-called ferromagnetic metal thin film type magnetic recording medium has been proposed,
It is getting attention. This ferromagnetic metal thin film type magnetic recording medium is not only excellent in coercive force and squareness ratio and excellent in electromagnetic conversion characteristics at short wavelengths, but it is also possible to make the thickness of the magnetic layer extremely thin so that recording demagnetization is possible. Also, there are various advantages such as a remarkably small thickness loss at the time of reproduction and an increase in the packing density of the magnetic material because it is not necessary to mix an organic binder which is a non-magnetic material in the magnetic layer.

However, in the above-mentioned ferromagnetic metal thin film type magnetic recording medium, since the smoothness of the magnetic layer surface is extremely good,
The substantial contact area becomes large, the adhesion phenomenon (so-called sticking) easily occurs, the friction coefficient becomes large, and the like, and there are many defects in durability and running property, and improvement thereof is a major issue. In general, a magnetic recording medium must be placed in a high-speed relative motion with a magnetic head in the process of recording / reproducing a magnetic signal, and at that time, the running must be performed smoothly and in a stable state. Further, it is preferable that wear and damage due to contact with the magnetic head be as small as possible.

Alternatively, since the magnetic layer is composed of a metal material,
During storage, especially when exposed to high temperature and high humidity, the surface of the magnetic layer is apt to corrode, which causes a problem that the saturation magnetization amount, the coercive force, etc. are deteriorated with time.

[Problems to be solved by the invention]

As described above, the ferromagnetic metal thin film type magnetic recording medium described above has many problems in practical properties such as runnability, durability, and corrosion resistance. Being tried.

However, it is difficult to say that these conventional trials are sufficient, and for example, the temperature range of the lubricants that have been widely used in the past is limited, and particularly in the low temperature range of 0 to −5 ° C. Also, there is a problem that many of them freeze, and the lubricating effect cannot be sufficiently exhibited.

The present invention is intended to further improve such practical characteristics, and is excellent in running property, durability, and corrosion resistance, and
It is an object of the present invention to provide a magnetic recording medium whose practical characteristics can be maintained even under a wide range of operating temperature conditions.

[Means for solving problems]

The inventors of the present invention, as a result of earnest research to achieve the above-mentioned object, show that the perfluoroalkylcarboxylic acid ester exhibits an excellent lubricating effect over a wide temperature range, and that the thiazole-based compound has improved corrosion resistance. Be valid for
Furthermore, they have found that the practical characteristics are synergistically improved by combining them, and have completed the present invention. That is, the present invention is characterized in that a ferromagnetic metal thin film is formed on a non-magnetic support, and the ferromagnetic metal thin film is coated with a protective film containing a perfluoroalkylcarboxylic acid ester and a thiazole-based compound as main components. It is what

The perfluoroalkylcarboxylic acid ester used in the present invention has the general formula C _n F _{2n + 1} COOR (wherein n represents an integer of 6 to 10 and R represents a carbon number of 9).
Represents ~ 25 hydrocarbon groups. ) And can be easily synthesized by reacting a perfluoroalkylcarboxylic acid with a corresponding alcohol.

In the above perfluoroalkylcarboxylic acid ester, the carbon number n of the perfluoroalkylcarboxylic acid moiety is
It is preferably in the range of 6-10. This carbon number n is 6
When it is less than the above range, the lubricating effect is insufficient, and conversely, when the number of carbons exceeds 10, solidification occurs in the low temperature range, and therefore the lubricating effect under the low temperature condition deteriorates. The same applies to the number of carbon atoms of the hydrocarbon group of the ester portion, and in the above general formula, the number of carbon atoms of the hydrocarbon group R is preferably 1 to 25, more preferably 9 to 25. . If the carbon-hydrogen group R has less than 9 carbon atoms, the lubricating effect is insufficient, and if it exceeds 25, the lubricating effect at low temperatures is lost. The hydrocarbon group R may be a long chain alkyl group, a branched alkyl group or an alkylene chain having a double bond.

On the other hand, the thiazole-based compounds used in the present invention include bismuthiol II, diazosulfide, azosulfim, 1,3,4-thiadiazole, bismuthiol, beazthiol, benzothiazole, 2-methylbenzothiazole, 2- (p-aminophenyl). -6-methylbenzothiazole, 2-mercaptobenzothiazole, benzothiazoline, 2-benzothiazoline, benzothiazolone and the like can be mentioned.

The mixing ratio of the above-mentioned perfluoroalkylcarboxylic acid ester and the thiazole-based compound is 10: 2 by weight.
It is preferably 10:10. In addition to the above-mentioned perfluoroalkylcarboxylic acid ester and thiazole compound, conventionally known lubricants and rust preventives may be used in combination.

As a method of adhering these perfluoroalkylcarboxylic acid ester and rust preventive (thiazole-based compound) to the ferromagnetic metal thin film, a solution obtained by dissolving the above perfluoroalkylcarboxylic acid ester and rust preventive in a solvent is used. It may be applied or sprayed on the surface of the ferromagnetic metal thin film, or conversely, the ferromagnetic metal thin film may be dipped in this solution and dried.

Here, the coating amount is preferably from ^{0.5mg / m 2 ~100mg / m 2} , and more preferably ^{1mg / m 2 ~20mg / m 2} .
If the coating amount is too small, the effects of lowering the friction coefficient, improving wear resistance, durability, and corrosion resistance will not be manifested, while if it is too large, clinging between the sliding member and the ferromagnetic metal thin film will occur. A phenomenon occurs, and on the contrary, driving performance deteriorates.

The magnetic recording medium to which the present invention is applied is one in which a ferromagnetic metal thin film is provided as a magnetic layer on a non-magnetic support. Here, as the material of the non-magnetic support, polyesters such as polyethylene terephthalate, Polyolefins such as polyethylene and polypropylene, cellulose derivatives such as cellulose triacetate, cellulose diacetate and cellulose acetate butyrate, vinyl resins such as polyvinyl chloride and polyvinylidene chloride, plastics such as polycarbonate, polyimide and polyamideimide,
Examples include light metals such as aluminum alloys and titanium alloys, and ceramics such as alumina glass. The form of this non-magnetic support may be any of film, sheet, disk, card, drum and the like.

The ferromagnetic metal thin film that is the magnetic layer is formed as a continuous film by a vacuum thin film forming technique such as a vacuum deposition method, an ion plating method, and a sputtering method.

In the above vacuum vapor deposition method, a ferromagnetic metal material is evaporated by resistance heating, high frequency heating, electron beam heating or the like under a vacuum of 10 ^-4 to 10 ^-8 Torr, and the evaporated metal (ferromagnetic metal material) is deposited on the disk substrate. In order to obtain a high coercive force, an oblique evaporation method in which the ferromagnetic metal material is obliquely evaporated on the substrate is adopted. Alternatively, the above vapor deposition is also included in order to obtain a higher coercive force.

The ion plating method is also a type of vacuum deposition method, and DC glow discharge or RF glow discharge is caused in an inert gas atmosphere of 10 ^-4 to 10 ^-3 Torr to evaporate the ferromagnetic metal material during discharge. It is to let.

The above-mentioned sputtering method is a method of causing a glow discharge in an atmosphere containing 10 ⁻³ to 10 ⁻¹ Torr of argon gas as a main component, and knocking out atoms on the target surface with the generated argon gas ions. DC 2
There are a polar and tripolar sputtering method, a high frequency sputtering method, a magnetron sputtering method using magnetron discharge, and the like. When this sputtering method is used, a base film of Cr, W, V or the like may be formed.

In any of the above methods, a base metal layer such as Bi, Sb, Pb, Sn, Ga, In, Cd, Ge, Si, and Tl is previously formed on the substrate by depositing it on the substrate surface. By forming the film in the vertical direction, a magnetic layer having no magnetic anisotropy orientation and excellent in-plane isotropy can be formed, which is suitable for a magnetic disk, for example.

When forming a metal magnetic thin film by such a vacuum thin film forming technique, Fe, Co,
In addition to Ni and other metals, Co-Ni alloys, Co-Pt alloys, Co-Ni-Pt
Alloy, Fe-Co alloy, Fe-Ni alloy, Fe-Co-Ni alloy, Fe-Co-
Examples thereof include B alloys, Co-Ni-Fe-B alloys, Co-Cr alloys, and those containing metals such as Cr and Al. Particularly, when a Co-Cr alloy is used, a perpendicular magnetization film is formed.

The thickness of the magnetic layer formed by such a method is 0.04
It is about 1 μm.

[Action]

The protective layer composed mainly of a perfluoroalkylcarboxylic acid ester and a thiazole-based compound adheres firmly to the ferromagnetic metal thin film, exerts a good lubricating effect to reduce the friction coefficient, and Prevent rusting. In particular, perfluoroalkylcarboxylic acid esters exhibit a good lubricating effect even at low temperatures, so that the operating temperature range can be expanded.

〔Example〕

Hereinafter, specific examples of the present invention will be described, but the present invention is not limited to these examples.

Synthesis Example 1. Nonadecafluorodecanoic acid isostearyl ester An ester reaction was carried out using isostearyl alcohol and nonadecafluorodecanoic acid in toluene and p-toluenesulfonic acid as a catalyst. That is, after heating under reflux for 1 hour, 3
Water was removed from the solvent over a period of time, and toluene was further removed under reduced pressure using an evaporator, followed by vacuum distillation for purification. (Note that isostearyl alcohol was synthesized by converting commercially available isostearic acid to n-butyl ester and then reducing it with lithium aluminum hydride.) The boiling point bp of the obtained fraction was 140 to 145 ° C / 0.2 mmHg. It was

In addition, the product was confirmed by infrared spectroscopy (IR), nuclear magnetic resonance analysis (NMR), and mass spectrometry (MASS). As a result, the absorption characteristic of the CF bond between 1210 and 1380 cm ⁻¹ , 17
80 cm ^-1 to the absorption of ester was observed absorption by stretching vibration of CH to 2910cm ^-1, and in the mass spectrum by chemical ionization method, since ^{the +} molecular ion peak M is seen in 765, to determine the structure.

Synthesis Example 2. Pentadecafluorodecanoic acid isostearyl ester By the same method as in Synthesis Example 1 above, isostearyl alcohol and pentadecafluorooctanoic acid in toluene,
The reaction was performed using p-toluenesulfonic acid as a catalyst.

bp 120 to 134 ° C (0.2 mmHg) IR 1200 to 1400 cm ^-1 1780 cm ^-1 2920 cm ^-1 M ⁺ 665 Synthesis example 3. Pentadecafluorooctanoic acid isononyl ester (CH ₃ ) ₃ C (CH ₂ ) CH (CH ₃ ) CH ₂ CH ₂ OCO (CF ₂ ) ₆ CF _{3 In} the same manner as in Synthesis Example 1 above, isononyl alcohol and pentadecafluorooctanoic acid were added to p-
The reaction was carried out using toluenesulfonic acid as a catalyst.

bp 94 ° C (0.2mmHg) IR 1210 to 1390cm ^-1 1785cm ^-1 2850 to 2960cm ^-1 M ⁺ 539 Synthesis example 4. Pentadecafluorooctanoic acid linoleyl ester CH ₃ (CH ₂ ) ₃ (CH ₂ CH = CH) ₂ (CH ₂ ) ₈ OCO (CF ₂ ) ₆ CF ₃ By the same method as in Synthesis Example 1 above, linoleyl alcohol and pentadecafluorooctanoic acid were added to p-
The reaction was carried out using toluenesulfonic acid as a catalyst.

bp 135~139 ℃ (0.2mmHg) was deposited with Co by ^{IR 1210~1380cm -1 1780cm -1 2850~3020cm -1 M} + 663 Example 14μm oblique deposition thick polyethylene terephthalate film, a film thickness of 1000Å strong A magnetic metal thin film was formed.

Next, on the surface of this ferromagnetic metal thin film, a perfluoroalkylcarboxylic acid ester (synthesized in the previous synthesis example) and a rust inhibitor (weight ratio 2: 1) shown in Table 1 were used as a solvent (acetone:
The solution diluted with ethyl ether = 1: 1) is applied at 10mg /
A sample tape was prepared by applying the coating solution so that the sample had a width of m ² and cutting it into a 1/2 inch width.

For each of the prepared sample tapes, the initial coercive force (Hc ₁ ) and saturation magnetization (Is ₁ ) and _{1 at} 45 ° C, 80% RH
After being left for a week, the coercive force (Hc ₂ ) and the saturation magnetization (Is ₂ ) were measured, and the rate of change thereof was calculated according to the following equation. As a comparative example, the change rate was also examined for a blank tape on which no protective layer was applied. The results are shown in Table 2.

Change rate of Hc = (Hc ₂ −Hc ₁ ) / Hc ₁ × 100 (%) Change rate of Is = (Is ₂ −Is ₁ ) / Is ₁ × 100 (%) It should be noted that no rust was found in each of the sample tapes of the examples, but considerable rust was found in the blank tape of the comparative example.

Next, for each of the prepared sample tapes, a temperature of 25
The coefficient of kinetic friction and shuttle durability were measured under the conditions of ℃, relative humidity (RH) 50%, and -5 ℃. This dynamic friction coefficient was tested by using a guide pin made of stainless steel (SUS304) with a constant tension and sending at a speed of 5 mm / sec. Further, the shuttle durability was evaluated by the number of shuttles until the output decreased by -3 dB after the shuttle traveled for 2 minutes each time. For still durability, the decay time of the output up to −3 dB in the paused state was evaluated. In addition, as a comparative example, a blank tape having no protective layer adhered was also measured. The results are shown in Table 3.

As is clear from this table, in each of the examples of the present invention, the coefficient of dynamic friction was small under each condition of room temperature and low temperature, the running was extremely stable, and the tape surface was not damaged even after running 100 times back and forth. I couldn't see it at all. Also, the durability was extremely good, and the output did not decrease by -3 dB even after 150 shuttles. On the other hand, in the tape of the comparative example having no protective layer, the coefficient of friction increased as the number of times of reciprocal traveling increased, the traveling was unstable, the tape was worn, and the durability was poor.

〔The invention's effect〕

As is clear from the above description, in the present invention, since the perfluoroalkylcarboxylic acid ester and the thiazole compound are used as the protective layer of the ferromagnetic metal thin film type magnetic recording medium, a significant improvement in practical characteristics is achieved. It is possible to obtain a magnetic recording medium having excellent running stability, wear resistance, and corrosion resistance.

Further, since the freezing point temperature of the perfluoroalkylcarboxylic acid ester is particularly low, the above-mentioned practical characteristics are ensured even when used at low temperatures, and it is possible to expand the operating temperature band of the magnetic recording medium.

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Claims (1)

[Claims] 1. A ferromagnetic metal thin film is formed on a non-magnetic support, and the ferromagnetic metal thin film has the general formula C _n F _{2n + 1} COOR (wherein n represents an integer of 6 to 10; Has 9 to 25 carbon atoms
Represents a hydrocarbon group of. ) Is a perfluorocarboxylic acid ester and a thiazole-based compound at 10: 2 to 10:10.
The magnetic recording medium is characterized in that a protective layer containing it at a mixing ratio is applied.