JPS62103839A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To maintain adhesiveness and lubricity and to improve wear resistance and running property by forming a thin ferromagnetic metallic film on a non- magnetic substrate and depositing a lubricating agent layer contg. a perfluoroalkylcarboxylate and higher alkyl sulfonic acid or the metallic salt thereof on the thin magnetic metallic film. CONSTITUTION:The thin ferromagnetic metallic film is formed on the non- magnetic substrate and the lubricating agent contg. the perfluoroalkylcarboxylate and higher alkyl sulfonic acid or the metallic salt thereof is deposited on the thin magnetic metallic film. The perfluoroalkylcarboxylate is expressed by the formula CnF2n+1COOR (where n denotes 6-10 integer, R denotes a hydrocar bon group of 1-25C) and is easily synthesized by bringing a per fluoroalkylcarboxylic acid and corresponding alcohol into reaction. The higher alkyl sulfonic acid or the metallic salt thereof is exemplified by 'Alkanol WXN(R)', 'Compound-8S(R)', etc. The amt. of the lubricating agent to be coated is preferably 0.5-100mg/m<2>.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention is directed to the production of ferromagnetic metal gil on a non-magnetic support by vacuum thin film forming techniques such as vacuum thin deposition and sputtering.
The present invention relates to a so-called ferromagnetic metal thin film type magnetic recording medium in which l* is formed as a magnetic layer.

[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 perfluoroalkyl carboxylic acid ester and a higher alkyl sulfonic acid or a metal thereof are added to the ferromagnetic metal thin film as the magnetic layer. Adhering salt as a lubricant, it provides excellent running performance over a wide range of operating temperature conditions.
Abrasion resistant.

This improves durability.

[Conventional technology]

Conventionally, as a magnetic recording medium, r
r-FezO++ containing Fe, o, Co
Fe, IO, r-Feg containing Fe, O, Co
Powder magnetic materials such as ferromagnetic powders such as ferrolide compounds of Oz and Fe, O, ferrolide compounds containing Co, oxide ferromagnetic powders such as Cry, or alloy magnetic powders whose main components are Fe, Co, Ni, etc. BACKGROUND ART Coating-type magnetic recording media are widely used, which are manufactured by applying and drying a magnetic paint dispersed in an organic binder such as a vinyl chloride-vinyl acetate copolymer, polyester resin, or polyurethane resin.

On the other hand, with the increasing demand for high-density magnetic recording, ferromagnetic metal materials such as Co-Ni alloys have been made into polyester by plating or vacuum thin film formation technology (vacuum evaporation, sputtering, ion blating, etc.). A so-called ferromagnetic metal thin film type magnetic recording medium, which is directly deposited on a non-magnetic support such as a film or a polyimide film, 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 a number of advantages, including extremely low thickness loss during playback and reproduction, and the ability to increase the packing density of the magnetic material because there is no need to mix a non-magnetic binder 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, running performance, etc., such as the substantial contact area becoming larger, adhesion phenomena (so-called sticking) becoming more likely to occur, and the coefficient of friction becoming larger, and improving these problems has become a major issue. In general, a magnetic recording medium is subjected to high-tracing relative motion with a magnetic head during the process of recording and reproducing magnetic signals, and must run smoothly and stably at this time. Further, it is better to minimize wear and damage caused by contact with the magnetic head.

For example, attempts have been made to improve the durability and runnability by applying a lubricant to the surface of the magnetic layer of the magnetic recording medium, that is, a ferromagnetic metal thin film to form a protective film.

[Problem that the invention seeks to solve]

By the way, when a protective film is formed by applying a lubricant as described above, this protective film exhibits good adhesion to the ferromagnetic metal thin film that is the magnetic layer and exhibits a high lubrication effect. This is required. .

Furthermore, these adhesion properties and lubrication effects must be excellent both under hot and humid conditions such as in the Kuha zone and subtropical regions, and under low temperature conditions such as in cold regions.

However, the operating temperature range of conventionally widely used lubricants is limited, and in particular, many of them become solid or freeze at low temperatures such as 0 to -5°C, so it is difficult to fully demonstrate their lubricating effect. I couldn't do that.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a magnetic recording medium that maintains adhesion and lubricity under any usage temperature conditions, has a small coefficient of friction, and has excellent wear resistance and runnability.

[Failure to solve the problem]

As a result of intensive research, the present inventors have determined that the above object can be achieved by using a long-chain alkyl group or an alkyl group having a double bond 5 or a branched alkyl group in the ester moiety of perfluoroalkylcarboxylic acid. The combination of perfluoroalkyl carboxylic acid ester and higher alkyl sulfonic acid or its metal salt exhibits superior lubricating effect compared to when used alone, and at the same time expands the operating temperature range. They discovered that it is possible to achieve this goal and completed the present invention, by forming a ferromagnetic metal thin film on a non-magnetic support,
A special feature of the present invention is that a lubricant layer containing a perfluoroalkyl carboxylic acid ester and a higher alkyl sulfonic acid or a metal salt thereof is coated on the ferromagnetic metal thin film.

The barfluoro[1-alkyl carboxylic acid ester used in the present invention has the general formula % (where n represents an integer of 6 to 10, and R' represents a hydrocarbon group having 1 to 25 carbon atoms. ), and 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 ~1o. This carbon number n is 6
If it is less than 2. The slipping effect is insufficient, and on the contrary, the number of carbon atoms is 10.
If the temperature exceeds 100%, the lubricant will solidify in the low temperature range, and the lubricating effect under low temperature conditions will therefore decrease. The same applies to the number of carbon atoms in the hydrocarbon group of the ester part, and in the above general 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 divided alkyl group, or an alkylene chain having a double bond.

On the other hand, as the higher alkyl sulfonic acid or its metal salt used in the present invention, for example, commercially available DuPont (duPont)
Pont) Alkanol WX
N, Du Pont compound (C
-83, Morton Chemical (Mo
Morphuni oil (Mor) manufactured by rtonChemica
pheoil) -X 479, and the like.

The blending ratio of the above-mentioned perfluoroalkyl carboxylic acid ester and higher alkyl sulfone M (or higher alkyl sulfonic acid metal salt) is from 30 to 7 by weight.
Preferably it is 0:30.

In addition to the above-mentioned perfluoroalkyl carboxylic acid ester and higher alkyl sulfonic acid (or higher alkyl sulfonic acid metal salt), conventionally known lubricants may be used in combination.

A method for attaching a lubricant layer containing these perfluoroalkyl carboxylic acid esters and higher alkyl sulfonic acids (or higher alkyl sulfonic acid metal salts) to a strong n-type metal thin film is to dissolve the above lubricant in a solvent. Should the obtained solution be applied or sprayed onto the surface of a ferromagnetic metal thin film, or conversely, a ferromagnetic metal thin film be placed in this solution? −
2. Just wash and dry.

Here, the application amount is 0.5■/, (~100mg
/d is preferable, and it is more preferable that it is 1 mg/m to 20 days/day. If the amount of this coating is too small, the effects of lowering the coefficient of friction and improving wear resistance and durability will not be achieved. On the other hand, if it is too much, a sticking phenomenon will occur between the sliding member and the ferromagnetic metal thin film. On the contrary, the running 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, and the material for the non-magnetic support may include polyesters such as polyethylene terephthalate, Polyolefins such as polyethylene and polypropylene, cellulose M such as cellulose triacetate, cellulose diacetate, 3 cellulose acetate butyrate, conductors, polyvinyl chloride,
Plastic resins such as polyvinylidene chloride, polycarbonate, polyimide, polyamideimide, etc.
Examples include 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,
It may be a disk, card, tram, etc.

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.

The above vacuum evaporation method involves heating a ferromagnetic metal material under a vacuum of 10-' to 10-' Torr by resistance heating, high-frequency heating, "JvL"
The evaporated metal (ferromagnetic metal material) is deposited on the disk substrate by evaporation using beam heating, etc.
Generally, in order to obtain a high coercive force, an oblique deposition method is employed in which the ferromagnetic metal material is deposited obliquely on a substrate. Alternatively, it also includes those in which the above-mentioned work is carried out in an oxygen atmosphere in order to obtain higher coercive force.

The above-mentioned ion blating method is also a type of vacuum thin deposition method, in which DC glow discharge and RF glow discharge are caused in an inert gas atmosphere of 10-4 to 10-3 Torr, and the above-mentioned ferromagnetic metal material is evaporated during the discharge. It is called zeru.

The above sputtering method uses 10-"l O-'Tor
A glow discharge is caused in an atmosphere mainly composed of argon gas, and the generated argon gas ions are used to knock out atoms on the target surface. , a high-frequency sputtering method, a magnetron sputtering method using magnetron discharge, etc.

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, the substrate is coated with Bi, Sb, Pb, Sn, Ga, and In.

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. It is suitable for forming a layer, for example, into a magnetic disk.

When forming a metal magnetic thin film using such vacuum thin film forming technology, the ferromagnetic metal materials used include Fe,
In addition to metals such as Co and Ni, Co-Ni alloy, Co-P
t alloy, Co-Ni-Pt alloy, Fe-Co alloy, Fe
Examples include -Ni alloy, Fe-Co-Ni alloy, Fe-Co-B alloy, Co-Ni-Fe-B alloy, Co-Cr alloy, or those containing metals such as Cr and 11. . In particular, when a Co--Cr alloy is used, a perpendicularly magnetized film is formed.

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

[Effect]

The lubricant layer containing perfluoroalkyl carboxylic acid ester and higher alkyl sulfonic acid or its metal salt firmly adheres to the ferromagnetic metal thin film, exhibits a good lubricating effect, and reduces the coefficient of friction. In particular, perfluoroalkyl carboxylic acid esters exhibit good lubricating effects even at low temperatures, and higher alkyl sulfonic acids or metal salts thereof exhibit good lubricating properties at room temperature, so that the temperature range of use 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 CL
(Cth) e-CH-Ct(2-OCO-(CFz
) 5cFz (CI+□), cl+.

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 then reducing it with lithium aluminum hydride.) The boiling point bp of the obtained fraction was 140-145°C, 10.2 mm, 11 g. there were.

Also, the product i[l? 2 is infrared spectroscopy (IR).

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

Synthesis Example 2゜Pentadecafluorodecanoic acid isostearyl ester C
113(C1l□)s-CH-CILz-OCO-(C
F2) 6CF3■ (C11□), CH3 In the same manner as in Synthesis Example 1 above, isostearyl alcohol and pentadecafluorooctanoic acid were added in toluene.
The reaction was carried out using p-1-luenesulfonic acid as a catalyst.

bp 120-134℃ (0.2 mml1mm1l
1200-1400cm-'1780cm-' 2920cm size M'' 665 Synthesis Example 3゜Pentadecafluorooctanoic acid isononyl ester (C
L) ,C(C112)C)1(C1h)CIl,CI
I□0CO(CFZ) 6CF3 In the same manner as in Synthesis Example 1 above, isononyl alcohol and pentadecafluorooctanoic acid were reacted in toluene using p-toluenesulfonic acid as a catalyst.

bp 94℃ (0.2mm) Ig) IR1210~
1390cm-'1785cn+-'2850-2960cm-' M゛ 539 Synthesis Example 4゜Pentadecafluorooctanoic acid sulfyl ester CH,
(co□> 3 (CIhC)I=CH) 2 (CI
lt) eoco(cpg), cp.

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℃ (0,2+uaHg)IR
1210 to 1380 cm-' 1780 cm-' 2850 to 3020 cm-'M'' 663 Example 1 Co is deposited on a 4 μm f'J polyethylene terephthalate film by an oblique evaporation method to form a ferromagnetic metal thin film with a thickness of 1000 mm. did.

Next, on the surface of this ferromagnetic metal thin film, perfluoroalkyl carboxylic acid ester (synthesized in the previous synthesis example) shown in Table 1 and higher alkyl sulfonic acid or its metal salt (weighted 1:1) were added as a solvent. A solution diluted with (Freon) was applied at a coating rate of 10 μm/d, and sample tapes were prepared by cutting into 1/2 inch width.

(Margin below) Table 1 For each of the sample tapes produced, the dynamic friction coefficient and shuttle durability were measured under the following conditions: 25°C, 50% relative humidity (RH), and -5°C. This dynamic friction coefficient was tested by using a guide pin made of stainless steel (SUS304) and feeding it at a speed of 5 mm/sec with a constant tension applied. In addition, the shuttle durability was evaluated by running the shuttle for 2 minutes each time, and the number of shuttles 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 to which no lubricant was applied was also measured.

The results are shown in Table 2.

Table 2 As is clear from this table, each of the examples of the present invention has a small dynamic friction coefficient under both room temperature and low temperature conditions, and runs smoothly and stably, even after 100 reciprocating runs. No damage to the tape surface was observed. 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 tape of the comparative example without a lubricant layer, the friction coefficient increased as the number of reciprocating runs increased, running was unstable, tape wear was observed, and durability was poor.

(Effects of the Invention) As is clear from the above description, in the present invention, a perfluoroalkyl carboxylic acid ester and a higher alkyl sulfonic acid or a metal salt thereof are used as a lubricant for a ferromagnetic metal thin film type magnetic recording medium. Therefore, the dynamic friction coefficient can be reduced under any temperature conditions, and a magnetic recording medium with excellent running stability and wear resistance can be obtained.

In particular, since the freezing point temperature of perfluoroalkyl carboxylic acid ester is low, it is highly effective when used at low temperatures.

Claims (1)

[Claims] A magnetic material characterized in that a ferromagnetic metal thin film is formed on a non-magnetic support, and a lubricant layer containing a perfluoroalkyl carboxylic acid ester and a higher alkyl sulfonic acid or a metal salt thereof is adhered to the ferromagnetic metal thin film. recoding media.