JPS62103828A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To maintain adhesiveness and lubricity and to improve wear resistance and runnability by forming a thin ferromagnetic metallic film on a nonmagnetic base and depositing a lubricating agent layer contg. a perfluoroalkylcarboxylate and fatty acid or the metallic salt thereof on the thin magnetic metallic film. CONSTITUTION:The thin ferromagnetic metallic film is formed on the nonmagnetic base and the lubricating agent contg. the perfluoroalkylcarboxylate and fatty 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 hydrocarbon group of 1-25C) and is easily synthesized by bringing a perfluoroalkylcarboxylic acid and corresponding alcohol into reaction. The fatty acid is exemplified by a satd. fatty acid and unsatd. fatty acid of 12-22C. The compounding ratio of the fatty acid or the metallic salt of the fatty acid is preferably 30:70-70:30wt. The amt. of the lubricating agent to be coated is preferably 0.5-100mg/m<2>.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a method of forming a strong n-type metal thin film as a magnetic layer on a non-magnetic support by vacuum thin film forming techniques such as vacuum evaporation and sputtering. The present invention relates to a so-called ferromagnetic metal 7il 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 nonmagnetic support, in which a perfluoroalkylcarboxylic acid ester and a fatty acid or a metal salt thereof are lubricated to the ferromagnetic metal thin film that is the magnetic layer. Adheres as a coating agent, providing excellent runnability and wear resistance over a wide range of operating temperatures.

This improves durability.

[Conventional technology]

Conventionally, as a magnetic recording medium, r
-F e toz, Co-containing r-F e20.
.

Fe1o+, r- containing F e , o, , G O
Fe Hertolide compound of e203 and Fe30a, C
Oxidation of bertolide compounds containing o, cro, etc.
v! A powder magnetic material such as IJ ferromagnetic powder or alloy magnetic powder mainly composed of Fe, Co, Ni, etc. is dispersed in an organic binder such as vinyl chloride-vinyl acetate copolymer, polyester resin, polyurethane resin, etc. Coated magnetic recording media, which are manufactured by applying and drying magnetic paint, are widely used.

In response to this, along with the demand for high-density magnetic recording, ferromagnetic metal materials such as Co-Ni alloys have been developed using plating and vacuum thin film forming techniques (vacuum evaporation, sputtering, ion blating, etc.). A magnetic recording medium of the so-called strong-A metal thin film type, which is directly deposited on a non-magnetic support such as a polyester 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, such as extremely small one-member loss in thickness during playback and reproduction, and the ability to increase the packing density of the magnetic material because there is no need to mix an organic binder, which is a non-magnetic material, into the magnetic layer. There is.

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 shortcomings in terms of durability and runnability, such as the actual contact area being large, making it easier for adhesion phenomena (so-called sticking) to occur, and increasing the coefficient of friction, and improving these issues is a major issue. In general, a magnetic recording medium is subjected to high-speed relative motion with a magnetic head during the recording and reproducing process of magnetic signals, and at this time, the traveling must be carried out smoothly and stably. It is better to have as little wear and damage as possible due to contact with magnetism.

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.

In addition, these adhesion properties and lubrication effects must be excellent both under hot and humid conditions, such as in tropical 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.

[Means for solving problems]

As a result of intensive research, the present inventors have found that the ester moiety of perfluorofurkylcarboxylic acid has a long chain alkyl group, an alkyl group having a double bond, and a branched alkyl group. By combining a perfluoroalkylcarboxylic acid ester into which one of the above is introduced and a fatty acid or a metal salt of a fatty acid, superior 71'I'l lubricating action is exhibited compared to when used alone, and at the same time, the operating temperature is They discovered that it is possible to expand the band and completed the present invention, in which a ferromagnetic metal thin film is formed on a nonmagnetic support, and perfluoroalkyl carbon is added to the ferromagnetic metal thin film. It is characterized by being coated with a lubricant layer containing an acid ester and a fatty acid or a metal salt thereof.

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 perfluorofurkylcarboxylic acid with the corresponding alcohol.

In the above perfluoroalkylcarboxylic acid ester, the number of carbon atoms n in the perfluoroalkylcarboxylic acid moiety is 6.
It is preferably in the range of ~lO. This carbon number n is 6
If the number of carbon atoms is less than 1 (Ll), the lubricating effect will be insufficient, and if the number of carbon atoms exceeds 10, the lubrication effect will be lowered. The same applies to the number of carbon atoms in the hydrocarbon group, 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 branched alkyl group, or an alkylene chain having a double bond.

On the other hand, the fatty acid used in the present invention has 1 carbon number.
Mention may be made of 2 to 22 saturated fatty acids and unsaturated fatty acids. Saturated fatty acids include lauric acid, tridecylic acid,
myristic acid, pentadecyl acid, valmitic acid, heptadecyl acid, stearic acid, nonadecanoic acid, arachidic acid,
Examples include eicosanoic acid, heneicosanoic acid, hehenic acid, and the like. Examples of unsaturated fatty acids include those having one or more unsaturated double bonds, such as dodecenoic acid, tetradecenoic acid, hexadecenoic acid, octadecenoic acid, oleic acid, elaidic acid, eicosenoic acid, tocosenoic acid, linoleic acid, and linuric acid. can be mentioned.

In addition, examples of fatty acid metal salts include lithium salts, sodium salts, potassium salts, magnesium salts, calcium salts, strontium salts, barium salts, iron salts, cobalt salts, nickel salts, copper salts, zinc salts, and aluminum salts of the fatty acids mentioned above. , lead salts, etc.

The blending ratio of the above-mentioned perfluoroalkyl carboxylic acid ester and fatty acid (or fatty acid metal salt) is preferably 30:0 to 70:30 by weight.
In addition to the above-mentioned perfluoroalkyl carboxylic acid ester and fatty acid (or fatty acid metal salt), conventionally known lubricants may be used in combination.

As a method for attaching a lubricant layer containing these perfluoroalkyl carboxylic acid esters and fatty acids (or fatty acid metal salts) to a ferromagnetic metal thin film, a solution obtained by dissolving the above lubricant in a solvent is applied to a ferromagnetic metal thin film. Should it be applied or sprayed onto the surface of a thin film, or vice versa? The ferromagnetic metal thin film may be immersed in the 8 liquid and dried.

Here, the coating amount is 0.5■/i~100■/n(
It is preferable that the coating amount is from 1■/d to 20■/a.If the coating amount is too small, the effects of lowering the friction coefficient and improving wear resistance and durability will not be achieved. On the other hand, if the amount is too large, a sticking phenomenon will occur between the sliding member and the ferromagnetic metal thin film, which will actually worsen running performance.

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, 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, sorting,
It may be a disk, card, drum, etc.

Further, the ferromagnetic metal thin film that is the magnetic layer is formed as a continuous film by a vacuum yiM4 formation technique such as a vacuum evaporation method, an ion blating method, or a sputtering method.

In the vacuum evaporation method, a ferromagnetic metal material is evaporated by resistance heating, high frequency heating, electron beam heating, etc. under a vacuum of 10-' to 10-1 Torr, and a thin metal (ferromagnetic metal material) is deposited on a disk substrate. Generally, in order to obtain a high resistance and n-force, an oblique deposition method is employed in which the ferromagnetic metal material is deposited obliquely to the substrate. Alternatively, it also includes those in which the vapor deposition is performed in an oxygen atmosphere in order to obtain higher coercive force.

The above-mentioned ion blating method is also a vacuum evaporation method.

The ferromagnetic metal material is evaporated during the discharge by causing DC glow discharge or RF glow discharge in an inert gas atmosphere of 10 −4 to 1 O−” Torr.

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. 2-pole, 3-pole sputtering method, high frequency sputtering method,
Alternatively, there is a magnetron sputtering method using magnetron discharge.

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

A base film such as (2) 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 forming the film from a direction perpendicular to the substrate surface, excellent magnetic properties can be achieved in the in-plane direction 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, C0-Ni alloy, Co-P
L gold alloy Co-N1-p alloy, Fe-Co alloy, Fe
Examples include -Ni alloy, Fe-Co-Ni alloy, Fe-Co-B alloy, Co-N1-Fe-B alloy, Co-Cr alloy, or those containing metals such as Cr and Al1. 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]

A lubricant layer containing a perfluoroalkyl carboxylic acid ester and a fatty acid or a metal salt thereof 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 fatty acids or metal salts thereof exhibit good lubricating properties at room temperatures, so that the temperature range of use can be expanded.

(Examples) 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
(C11□)8-C1l-CIl□-0CO-(CFz
) BCF3(CH2)&C1+1 An ester reaction was carried out between isostearyl alcohol and nonadecafluorodecanoic acid in toluene using p-)luenesulfonic acid as a catalyst. That is, after heating under reflux for 1 hour, 3
Water in the solvent was removed over time, and toluene was removed using an evaporator under residual pressure, followed by vacuum distillation for purification. (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.

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, an absorption peculiar to the CF bond was observed from +210 to 1380 cm-', an ester absorption at 1780 cm-', and an absorption due to the stretching vibration of CH at 2910 cm-'.In addition, in the mass spectrum using 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
H:+(C)Iz)g-CI(-CHz-OCO-(C
Fz)acF3(CHz)aC)I:+ 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)I
R1200-1400cm-'1780cm-'2920cm-'M' 665 Synthesis Example 3゜Pentadecafluorooctanoic acid isononyl ester (C
Hff) 3C(CH2)CI((CH3)CH2CH
2OCO (CF Ri &CF!) Isononyl alcohol and pentadecafluorooctanoic acid were reacted with toluene+Lp-)luenesulfone [-M medium and L-1' in the same manner as in Synthesis Example 1 above.

bp 94℃ (0.2mdg) [R1210~1390cm-'1785c+
w-' 2850-2960 cm-'M''' 539 Synthesis Example 4 Benkde's fluorooctanoic acid sulfuryl ester CIl
ff (C11□)i (CII□C11=CI+)
2 (CI+□)80CO(CF, ), CF.

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

bp 135-139℃ (0.2mm) Ig)IR
1210-1380 cm-' 1780 cm+-' 2850-3020 cm-'M'' 663 Example 1 CO was deposited on a polyethylene terephthalate film with a thickness of 4 μm by an oblique evaporation method to form a ferromagnetic metal thin film with a thickness of 1000 cm.

Next, on the surface of this ferromagnetic metal thin film, perfluoroalkylcarboxylic acid ester (synthesized in the previous synthesis example) shown in Table 1 and fatty acid or its metal salt (weight ratio 1:1) were applied.
A coating amount of a solution diluted with a solvent (Freon) is 10 /
A sample tape was prepared by applying it so as to form an ITr and cutting it into a 1/2 inch width.

(Left below) Table 1 For each sample tape produced, the temperature was 25"C3.
The dynamic friction coefficient and shuttle durability were measured under conditions of relative humidity (R)i) 50% and -5°C. This dynamic friction coefficient was determined by applying a constant tension to 5 mm1s using a guide bottle made of stainless steel (StJS304).
The test was carried out at a speed of EC. In addition, shuttle durability was determined by running the shuttle for 2 minutes each time.
Evaluation was made by 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.

(Leaving space below) Table 2 As is clear from this table, each of the examples of the present invention has a small dynamic friction coefficient under the conditions of room temperature, 2 low temperature, extremely stable running, and 100 cycles of reciprocation. Even after running, 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, with the comparative tape without a lubricant layer, the coefficient of friction increases as the number of reciprocating runs increases, running is unstable, tape wear is observed, and durability is poor. there were.

[Effects of the Invention] As is clear from the above description, in the present invention, perfluoroalkylcarboxylic acid esters and fatty 111i acids or metal salts thereof are used as lubricants for magnetic recording media of thin film type. Since it is used, the coefficient of dynamic friction 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] 1. A magnetic recording medium comprising: a ferromagnetic metal thin film formed on a nonmagnetic support; and a lubricant layer containing a perfluoroalkylcarboxylic acid ester and a fatty acid or a metal salt thereof coated on the ferromagnetic metal thin film.