JPS62117132A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain the titled magnetic recording medium having excellent traveling stability and resistance to wear and corrosion by using a perfluoroalkylcarboxylic acid ester and a compd. having a mercapto group as a protective layer. CONSTITUTION:A ferromagnetic metallic thin film is formed on a nonmagnetic carrier, and the protective layer consisting essentially of a perfluoroalkylcarboxylic acid ester and a compd. having a mercapto group is coated on the ferromagnetic metallic thin film to obtain the medium. The perfluoroalkylcarboxylic acid ester to be used is shown by the formula, CnF2n+1COOR (where n is a 6-10 integer and R is a 1-25 C hydrocarbonic group), and can be easily synthesized by the reaction of a perfluoroalkylcarboxylic acid with the corresponding alcohol. 2- benzooxazolethiol, etc., can be exemplified as the compd. having a mercapto group and used as a rust preventive agent. The compounding ration by weight of the perfluoroalkylcarboxylic acid ester to the compd. having a mercapto group is preferably controlled to 10/2-10/10.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a magnetic layer in which a ferromagnetic metal thin film is formed as a magnetic layer on a non-magnetic support by a vacuum gj film forming technique such as vacuum evaporation or sputtering. The present invention relates to a so-called ferromagnetic metal thin film type magnetic recording medium.

[Summary of the invention]

The present invention provides a magnetic recording medium in which a ferromagnetic metal thin film is formed as a magnetic layer on a non-magnetic support, in which a compound having a perfluoroalkyl carboxylic acid ester and a mercapto group is mainly used in the ferromagnetic metal thin film as the magnetic layer. By applying a protective layer as a component, it is intended to improve running performance, abrasion resistance, durability, and corrosion resistance.

[Conventional technology]

Conventionally, as a magnetic recording medium, T-
r FezOr+Fes containing FezOz+GO
Fe x Oa containing O4+ Co, r −F
e Hertolide compound of zo* and FeyOa, G
Powders such as ferromagnetic powders of oxides such as ferromagnetic powders, such as ferromagnetic powders containing o, or alloy magnetic powders whose main components are Fe, Co, Ni, etc. Coating-type magnetic recording media are widely used, which are manufactured by coating and drying a magnetic paint dispersed in an organic binder such as a polyester resin or a polyurethane resin.

On the other hand, with the increasing demand for high-density magnetic recording, ferromagnetic metal materials such as Co-Ni alloys can be made into polyester by plating or vacuum thin film formation technology (vacuum evaporation method, sputtering method 1, ion blating method, etc.). So-called ferromagnetic metal 'i! A J-film type magnetic recording medium has been proposed and is attracting attention. This ferromagnetic metal thin film type magnetic recording medium not only has excellent coercive force and squareness ratio, and has excellent electromagnetic conversion characteristics at short wavelengths, but also has the ability to make the thickness of the magnetic layer extremely thin, making recording demagnetization possible. It has many advantages, such as extremely small thickness loss during playback and reproduction, and the ability to increase the packing density of the magnetic material since there is no need to mix an organic binder, which is a non-magnetic material, into the magnetic layer.

However, in the above-mentioned ferromagnetic metal thin film type magnetic recording medium, since the surface smoothness of the magnetic layer is extremely good,
There are many drawbacks in terms of durability, runnability, etc., such as an increase in the actual contact area, a tendency to cause adhesion (so-called sticking), and an increase in the coefficient of friction, and improvement of these problems has become a major issue. In general, magnetic recording media are subjected to high-speed relative motion with magnets during the process of recording and reproducing magnetic signals, and must run smoothly and stably during this time. Also, it is better to minimize wear and damage caused by contact with the magnetic head.

Alternatively, since the magnetic layer is made of a metal material,
During storage, especially when exposed to high temperature and high humidity, corrosion tends to occur on the surface of the magnetic layer, which causes problems such as saturation magnetization, coercive force, etc., deteriorating over time.

[Problem that the invention seeks to solve]

As described above, the above-mentioned ferromagnetic metal thin film type magnetic recording media has many problems in practical properties such as runnability, durability, and corrosion resistance. is being attempted.

However, these conventional attempts are still far from satisfactory.For example, the operating temperature range of conventionally widely used lubricants is limited, and in particular, at low temperatures such as O to -5℃, solid Otherwise, there is a problem that many of the materials freeze, and the lubricating effect cannot be sufficiently exerted.

The purpose of the present invention is to further improve such practical characteristics, and to develop a magnetic recording medium that has excellent runnability, durability, and corrosion resistance, and which maintains these practical characteristics even under a wide range of operating temperatures. For the purpose of providing.

[Means for solving problems]

In order to achieve the above-mentioned object, the present inventors conducted extensive research and found that perfluoroalkylcarboxylic acid esters exhibit excellent lubricating effects over a wide temperature range, and that compounds containing mercapto-5 have corrosion resistance. The present invention has been completed based on the discovery that the present invention is effective in improving the properties of the present invention, and that practical characteristics can be synergistically improved by combining these. That is, the present invention involves forming a ferromagnetic metal thin film on a non-magnetic support, and coating a protective layer containing a perfluoroalkyl carboxylic acid ester and a compound having a mercapto group as main components on the magnetically ferromagnetic metal thin film. It is characterized by the fact that

The perfluoroalkyl carboxylic acid ester used in the present invention has the general formula % (in the formula, n represents an integer of 6 to 10, and R represents a hydrocarbon group having 1 to 25 carbon atoms). It can be easily synthesized by reacting a perfluoroalkylcarboxylic acid with a corresponding alcohol.

In the above perfluoroalkylcarboxylic acid ester, the number of carbon atoms n in the perfluoroalkylcarboxylic acid moiety is 6.
It is preferable that it is in the range of ~10. This carbon number n is 6
If the number of carbon atoms is less than 10, the lubricating effect will be insufficient, and if the number of carbon atoms exceeds 10, the lubricating effect under the low temperature strip 41 will decrease. Also, the same applies to the number of carbon atoms in the hydrocarbon group of the ester part, and in the previous one-ship formula,
The hydrocarbon group R preferably has 1 to 25 carbon atoms, more preferably 9 to 25 carbon atoms.

If the number of carbon atoms in the hydrocarbon group R is less than 9, the lubricating effect will be insufficient, and if it exceeds 25, the lubricating effect at low temperatures will be lost. Note that this 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, examples of compounds having a mercapto group used as a rust preventive in the present invention include 2-benzoxazolethiol, thiophenol, 2-propanethiol thiosalicylate, and thiouracil.

2.3-quinoxaline dithiol, dithizone, thioxin, 2-benzimidazolethiol, 6-thioguanine, 5-nitro-2-benzimidazolethiol,
Examples include 5-amino-1,3,4-thiazole-2-thiol.

The mixing ratio of the perfluoroalkyl carboxylic acid ester and the compound having a mercapto group is preferably 10:2 to 10:10 by weight. In addition to the above-mentioned perfluoroalkyl carboxylic acid ester and compound having a mercapto group, conventionally known lubricants and rust preventives may be used in combination.

A method for attaching these perfluoroalkyl carboxylic acid esters and rust inhibitors (compounds having mercapto groups) to a strong f-type metal thin film is to dissolve the perfluoroalkyl carboxylic acid esters and rust inhibitors in a solvent. The obtained solution may be applied or sprayed onto the surface of the ferromagnetic metal thin film, or conversely, the ferromagnetic metal thin film may be immersed in this solution and dried.

Here, the amount of application is 0.5■/r! (~100 days/
lI (preferably, 1 s/d to 20 s/i). If this coating amount is too small, the coefficient of friction will decrease, and the wear resistance and durability will deteriorate.

The effect of improving corrosion resistance is not apparent, and on the other hand, if the amount is too large, a phenomenon of sticking occurs between the sliding member and the IAI magnetic metal thin film, and running properties are deteriorated on the contrary.

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, and the material for the non-magnetic support may include 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, polycarbonate,
Examples include plastics such as polyimide and polyamideimide, light metals such as aluminum alloys and titanium alloys, and ceramics such as alumina glass.

The forms of this non-magnetic support include film, sheet,
Disc, card? Any such as rum may be used.

Further, 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 evaporation method, an ion blating method, or a sputtering method.

In the vacuum evaporation method described above, a ferromagnetic metal material (N-1) is evaporated by resistance heating, high-frequency heating, electron beam heating, etc. under a vacuum of 10-"~10-" Torr, and the evaporated metal (strong In order to obtain a high coercive force for -M, an oblique evaporation method is employed in which the ferromagnetic metal material is deposited obliquely to the substrate. Alternatively, in order to obtain higher coercive force, it also includes those in which the tea ceremony is carried out in an oxygen atmosphere.

The above-mentioned ion brating method is also a type of vacuum evaporation method, in which DC glow discharge and RF glow discharge are caused in an inert gas atmosphere of 1O-4 to 10-3 Torr, and the above-mentioned ferromagnetic metal material is evaporated during the discharge. That is what it is.

The above sputtering method involves causing glow discharge in an atmosphere mainly composed of argon gas at 101 to 10-'Torr, and using the generated argon gas ions to knock out atoms on the target surface. ? Examples include R2-pole sputtering, triple-pole sputtering, high-frequency sputtering, and magnetron sputtering using magnetron discharge.

In the case of this sputtering method, Cr or W is used.

A base film such as V may be formed in advance.

In any of the above methods, Bi, Sb, Pb, Sn, Ga, and In are preliminarily deposited on the substrate.

By pre-depositing a base metal layer such as Cd, Ge, Si, T1, etc., and depositing the film in a direction perpendicular to the substrate surface, excellent magnetic properties can be achieved in an in-plane manner without magnetic anisotropy orientation. The ferromagnetic metal material used when forming a metal magnetic thin film by the vacuum thin film forming technology, which is suitable for forming a magnetic disk, for example, is Fe, Co, etc. In addition to metals such as , Ni, C0-Ni
alloy, Go-Pt alloy, Co-Ni-Pt alloy, Fe-
Co alloy, Fa-Ni alloy, Fe-Co-Ni alloy, F
e-Co-B alloy, Co-N1-Fs-B alloy, Co-
Examples include Cr alloys and Cr alloys containing metals such as Cr and /1F2. In particular, when a Co--Cr alloy is used, a perpendicularly magnetized film is formed.

1 of the magnetic layer formed by such a method! Thickness is 0
．． It is about 0.04 to 1 μm.

[Effect]

The protective layer, which is mainly composed of a perfluoroalkyl carboxylic acid ester and a compound having a mercapto group, firmly adheres to the ferromagnetic metal thin film7, exhibits a good lubricating effect, reduces the coefficient of friction, and 6 Preventing Rust in Metal Thin Films In particular, perfluoroalkyl carboxylic acid esters exhibit a good lubricating effect even at low temperatures, so the temperature range in which they can be used can be expanded.

[Examples] Specific examples of the present invention will be described below, but the present invention is not limited to these examples.

Synthesis Example 1゜Nonadecafluorodecanoic acid isostearyl ester CH
3(CHz) 5-CH-CHz-OCO(CFz)
*CFz(CHi) &CH.

An ester reaction was carried out between isostearyl alcohol and nonadecafluorodecanoic acid in toluene using p-toluenesulfonic acid as a catalyst. That is, after heating under reflux for 1 hour, 3
Water in the solvent was removed over time, toluene was removed under reduced pressure using an evaporator, and the mixture was purified by vacuum distillation. (Isostearyl alcohol was synthesized by converting commercially available isostearic acid into n-butyl ester and reducing it with lithium aluminum hydride.) The boiling point bp of the obtained fraction was 140 to 145°C and 10.2 mdg. Ivy.

In addition, the product can be confirmed by infrared spectroscopy (IR).

The analysis was carried out by nuclear magnetic resonance analysis (NMR) and mass spectrometry (MASS). As a result, absorption by CF bond spectra from 1210 to 1380 cm-', absorption by ester at 1780 cm-', and absorption due to stretching vibration of CH at 2910 cm-' were observed.In addition, in the mass spectrum by the chemical ion method, the molecular ion peak This structure was determined because M' is found in 765.

Synthesis Example 2゜Pentadecafluorodecanoic acid isostearyl ester C
H:+(CHz) e-CH-CHz-OCO(CFz
) 6CF:1(CHt) -C[+3 By the same method as in Synthesis Example 1 above, isostearyl alcohol and pentadecafluorooctanoic acid were added in toluene.
The reaction was carried out using p-toluenesulfonic acid as a catalyst.

bp 120-134℃ (0.2mmHg) IR1
200-1400cm-'1780cm-'2920cm-'M' 665 Synthesis Example 3゜Pentadecafluorooctanoic acid isononyl ester (C
H3) zc(CHz)CH(Ct13)CHzC)I
JCO(CFz), cp.

By the same method as in Synthesis Example 1 above, isononyl alcohol and pentadecafluorooctanoic acid were mixed in toluene with p-
The reaction was carried out using toluenesulfonic acid as a catalyst.

bp 94℃ (0.2mmHg) IR1210-1390cm-'1785cm-'2850-2960cm-'M" 539 Synthesis Example 4゜Pentadecafluorooctanoic acid sulfur ester CHz
(CL) s (CHtCH-CH)t (CL)
aOcO(Ch) hcFs By the same method as in Synthesis Example 1 above, rillyl alcohol and pentadecafluorooctanoic acid were reacted in toluene using p-toluenesulfonic acid as a catalyst.

bp 135-139℃ (0.2mm) Ig)IR
1210~1380 cm-' 1780 cm-' 2850-3020 cm-'M'' 663 Example 14 Co is coated on a polyethylene terephthalate film of r!ml'X by an oblique vapor deposition method, and the film thickness is 1000 cm.
A ferromagnetic gold r% thin film was formed.

Next, on the surface of this ferromagnetic metal thin film, perfluoroalkylcarboxylic acid esters (synthesized in the previous synthesis example) shown in Table 1 (A) and Table 1 (B) and a rust inhibitor (weight ratio 2
A solution obtained by diluting :1) with a solvent (acetone:ethyl ether=i:i) was applied at a coating amount of 10 μ/M, and the sample tape was cut into 1/2 inch width.

(Left below) Table 1 (A) Table 1 (B) Initial holding power (
Hc+) and saturation magnetization! (Is+), and 45°C.

After being left under 80% RH for one week, the coercive force (llc2) and saturation magnetization ft (Isz) were measured, and the rate of change was determined according to the following formula. As a comparative example, the rate of change was also investigated for a blank tape on which no protective layer was applied.

The results are shown in Table 2.

Rate of change in Hc - (I(c+-Hcz)/Hc+X100
(χ) Rate of change of Is” (Is+ (st> / I
s+ xloo(z) (hereinafter referred to as margins) Table 2 Note that no rust was observed in each of the sample tapes of the Examples, but a considerable amount of rust was observed in the blank tapes of the Comparative Examples.

Next, for each sample tape produced, a temperature of 25
℃, relative humidity (RH) 50%, and -5℃ conditions F
The dynamic friction coefficient and shuttle durability were measured. This dynamic friction coefficient is determined by using a guide bottle made of stainless steel (SUS304) and applying a constant tension to 5 n+s+/
The test was carried out by feeding at a speed of . In addition, the shuttle durability was evaluated by running the shuttle for 2 minutes each time, and determining the number of shuttle runs until the output decreased by 13 dB.

Still durability was evaluated by evaluating the decay time for the output to -3 dB in a pause state. As a comparative example, a blank tape without any protective layer was also measured. The results are shown in Table 3 (A) and Table 3 (B).

(Margins below) Table 3 (A) Table 3 (B) As is clear from this table, each example of the present invention has a small dynamic friction coefficient under both normal temperature and low temperature conditions, and the running is extremely stable. Moreover, even after running back and forth 100 times, no damage was observed on the tape surface. Furthermore, the durability was extremely good, and even after 150 shuttle runs, no decrease in output by 13 dB was observed. On the other hand, in the comparative tape without a protective layer, the friction coefficient increased as the number of reciprocating runs increased, running was unstable, tape wear was observed, and durability was poor.

〔Effect of the invention〕

As is clear from the above explanation, in the present invention, since a compound having a perfluoroalkyl carboxylic acid ester and a mercapto group is used as a protective layer of a ferromagnetic metal thin film type magnetic recording medium, practical characteristics are significantly improved. This makes it possible to improve the magnetic recording medium, thereby providing a magnetic recording medium with excellent running stability, wear resistance, and corrosion resistance.

In addition, since the freezing point temperature of perfluoroalkyl carboxylic acid ester is particularly low, the above-mentioned practical characteristics are ensured even when used at low temperatures, making it possible to expand the operating temperature range of the magnetic recording medium.

Claims (1)

[Claims] Magnetic recording characterized in that a ferromagnetic metal thin film is formed on a nonmagnetic support, and a protective layer containing a perfluoroalkyl carboxylic acid ester and a compound having a mercapto group as a main component is applied to the ferromagnetic metal thin film. Medium.