JPS62117126A - 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 naphthols as a protective layer. CONSTITUTION:A ferromagnetic metallic thin film is formed on a nonmagnetic carrier, and the protective layer consisting essentially of a perfluo roalkylcarboxylic acid ester and naphthols is coated on the ferromagnetic metal lic thin film to obtain the medium. The perfluoroalkylcarboxylic acid ester to be used is expressed 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. alpha-naphthol, etc., can be exemplified as the naphthols to be used. The compounding ratio by weight of the perfluoroalkylcarboxylic acid ester to the naphthols is preferably controlled to 10/2-10/10.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a so-called magnetic layer in which a ferromagnetic metal thin film is formed 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 ferromagnetic metal thin film type magnetic recording medium.

[of the invention (desired)]

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 ferromagnetic metal yi film as a magnetic layer contains perfluoroalkyl carboxylic acid ester and naphthol as main components. By applying a protective layer to the surface of the vehicle, it is intended to improve running properties, abrasion resistance, durability, and corrosion resistance.

[Conventional technology]

Conventionally, as a magnetic recording medium, r-
rFezO5+Fe3 containing Fe, O,, Co
04+ Fe 30a+ r −F containing Co
e zo.

Powder magnetic materials such as ferromagnetic powders such as ferromagnetic powders such as ferromagnetic powders such as ferromagnetic powders such as ferromagnetic powders such as ferromagnetic powders such as ferromagnetic powders such as ferromagnetic powders containing Co and ferrolide compounds containing Fe30a and Fe30a, etc., are converted into vinyl chloride-vinyl acetate. 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 copolymer, polyester resin, or polyurethane resin.

On the other hand, with the increasing demand for high-quality 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, iodine brating method, 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 and density of magnetic materials since there is no need to mix a non-magnetic organic 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, 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. Generally, in the process of recording and reproducing magnetic signals, a tn magnetic recording medium is subjected to high-speed relative motion with a magnetic head, 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.

Alternatively, since the magnetic layer is made of a metal material,
During storage, especially when exposed to high temperatures or high temperatures, corrosion tends to occur on the surface of the magnetic layer, resulting in problems such as the saturation magnetization, coercive force, etc. being deteriorated orally.

[Problem that the invention seeks to solve]

As described above, the above-mentioned ferromagnetic metal thin film magnetic recording media have 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 0 to -5℃, solid Otherwise, there is a problem that many of the materials freeze, and the lubricating effect cannot be sufficiently exerted.

The present invention aims to further improve such practical characteristics, and has excellent running properties, durability, and corrosion resistance, and
The object of the present invention is to provide a magnetic recording medium that maintains these practical characteristics even under a wide range of operating temperatures.

c. Means for Solving Problems] The present inventors have conducted extensive research to achieve the above-mentioned objectives, and have found that perfluoroalkyl carboxylic acid esters exhibit excellent lubricating effects over a wide temperature range. Furthermore, the inventors have discovered that naphthols are effective in improving corrosion resistance, and that practical properties can be synergistically improved by combining these, leading to the completion of the present invention.

That is, the present invention is characterized in that a ferromagnetic metal thin film is formed on a nonmagnetic support, and a protective layer containing perfluoroalkyl carboxylic acid ester and naphthol as main components is applied to the ferromagnetic metal thin film. It is something to do.

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.
The number of carbon atoms n is preferably in the range of ~IO.
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, it will solidify in a low temperature range, resulting in a decrease in the lubricating effect under low temperature conditions. The same applies to the number of carbon atoms in the hydrocarbon group of the ester moiety, and in the above general formula, it is preferable that the number of carbon atoms in the hydrocarbon group R is 1 to 25.
More preferably, it has 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 forming a double bond.

On the other hand, the naphthols used in the present invention include α-
Naphthol, β-naphthol, 1,2-naphthalene diol, 1,3-naphthalene diol, 1,4-naphthalene diol, 1,5-naphthalene diol.

Pure naphthols such as 1.7-naphthalenediol, 1.8-naphthalenediol, 2,3-naphthalenediol, 1,4.5-naphthalenetriol, 1.2,5.8-naphthalenetetraol, and nitro, Nitroso-, amino-, halogeno-substituted naphthols, such as 1-chloro-2-naphthol, 2,4-dichloro-1-naphthol, 1-nitro-2-naphthol, 1,6-sinitro-2-naphthol, 1-nitroso-2-naphthol -naphthol, 2-
Examples include nitroso-1-naphthol, -amino-2-naphthol, and the like.

The blending ratio of the above-mentioned perfluoroalkyl carboxylic acid ester and naphthols is 10=2 to x in weight ratio.
o:to is preferred. In addition to the above-mentioned perfluoroalkyl carboxylic acid esters and naphthols,
Conventionally known lubricants and rust preventives may be used in combination.

As a method for attaching these perfluoroalkyl carboxylic acid esters and rust inhibitors (naphthols) to a ferromagnetic metal thin film, a solution obtained by dissolving the above perfluoroalkyl carboxylic acid esters and rust inhibitors in a solvent is strongly The solution may be applied or sprayed onto the surface of the magnetic metal thin film, or conversely, the ferromagnetic metal thin film may be immersed in this solution and dried.

Here, the coating amount is 0.5111g/rd~10
It is preferable that it is 0■/d, and 1 mg/rd to 2
More preferably, it is 0 ■/bo. If the amount applied is too small, the friction coefficient will decrease, 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 ferromagnetic 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, plastics such as polycarbonate, polyimide, and polyamideimide, and aluminum. Examples include alloys, light metals such as titanium alloys, and ceramics such as alumina glass.

The forms of this non-magnetic support include film, sheet,
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 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 is evaporated by resistance heating, high frequency heating, electron beam heating, etc. under a vacuum of 10-4 to 10-'' Torr, and the evaporated metal (
Generally, in order to obtain a high coercive force, an oblique evaporation method is employed in which the ferromagnetic metal material is deposited obliquely to the substrate. or,
It also includes those in which the above-mentioned vapor deposition is performed in an oxygen atmosphere in order to obtain higher coercive force.

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

The above sputtering method uses 10-' to 10-' Torr.
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. method, or 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 the direction perpendicular to the substrate surface, it is possible to achieve excellent in-plane method without N'm anisotropic orientation. It is possible to form a magnetic layer with a magnetic layer, and is suitable for use in, for example, a magnetic disk.

When forming a metal magnetic thin film using such vacuum 1M forming technology, the ferromagnetic metal materials used include Fe,
In addition to metals such as Co and Ni, C.

-Ni alloy, -Co-Pt alloy, Co-Ni-Pt alloy, Fe-Co alloy, Fe-Ni alloy, Fe-Co-Ni
Examples include alloys, Fe-Co-B alloys, Go-Ni-Fe-B alloys, Co-Cr alloys, and those containing metals such as Cr and A1. 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 protective layer, which is mainly composed of perfluoroalkyl carboxylic acid ester and naphthols, firmly adheres to the ferromagnetic metal thin film, exhibits a good lubricating effect, reduces the coefficient of friction, and is highly effective against ferromagnetic metal thin films. prevent the occurrence of In particular, perfluoroalkyl carboxylic acid esters exhibit a good lubricating effect even at low temperatures, so that the temperature range in which they can be used 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 CI
+3(CHJe-CH-CHz-OCO(CFx)++
CFs(CHz)*CHz 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 1.40-145℃10,2 It was mmHg.

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, 1210~1380cn+-'
There is an absorption characteristic of the CF bond at 1780 cm, an absorption due to the stretching vibration of CM at 2910 cm, and a molecular ion peak M can be seen at 765 in the chemical ion method mass spectrum. We decided on this structure.

Synthesis Example 2゜Pentadecafluorodecanoic acid isostearyl ester C
H1(C1(z)s-C)I-CHz-OCO(CPz
) bcF3(CL) bCHs By the same method as in Synthesis Example 1 above, isostearyl alcohol and pentadecafluorooctanoic acid were added in toluene.
The reaction was catalyzed by p-) toluenesulfonic acid.

bp 120-134℃ (0.2mmHg) IR1
200-1400cm-'1780cm-'2920cm"'M' 665 Synthesis Example 3゜Pentadecafluorooctanoic acid isononyl ester (C
L) :+C(CHdCH(CH3)CHzCHtOC
O(Ch) ach By the same method as in Synthesis Example 1 above,
Isononyl alcohol and pentadecafluorooctanoic acid were reacted in toluene using p-toluenesulfone a as a catalyst.

bp 94℃ (0.2mmHg) IR1210~1390cm-'1785cm
-'2850-2960cs+-'M" 539 Synthesis Example 4゜Pentadecafluorooctanoic acid sulfyl ester CH2
(C)l 3 (CHlC)I=CH)! (C1
+ri 5Oco (cps) 6CFsBy the same method as in Synthesis Example 1 above, lilyl alcohol and pentadecafluorooctanoic acid were reacted in toluene using p-)luenesulfonic acid as a catalyst.

bp 135-139℃ (0,2+wwHg)IR
1210~1380cm-'1780cm-'2850~3020cm-'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 μm.

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-1=1) was applied at a coating amount of 10 .mu./M, and the sample tape was cut into a 1×2 inch width.

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

After being left under 80% RH for one week, the coercivity (tlc*) and saturation magnetization (Im) 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.

""IT conversion rate=(Hc+Hcz)/Hc+Xl0Q
(%) Rate of change in Is - (Is + l5z) / l5I
X100 (%) (blank below) Table 2 Note that rust was not observed in each of the sample tapes of the Examples, but considerable rust was observed in the blank tapes of the Comparative Examples.

Next, for each sample tape produced, a temperature of 25
The dynamic friction coefficient and shuttle durability were measured under the following conditions: °C, 50% relative temperature (RH), and -5 °C. This dynamic friction coefficient was determined by using a guide bottle made of stainless steel (SUS304) and applying a constant tensile strength of 5 mm/sec.
The test was conducted by feeding at a speed of e. 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 was below 13 dBi. 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. 3rd result
It is shown in Table (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, perfluoroalkyl carboxylic acid esters and naphthols are used as the protective layer of the ferromagnetic metal thin film type magnetic recording medium, so that the practical characteristics are significantly improved. This makes it possible to provide 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] 1. A magnetic recording medium comprising: a ferromagnetic metal thin film formed on a non-magnetic support; and a protective layer containing perfluoroalkyl carboxylic acid ester and naphthol as main components applied to the ferromagnetic metal thin film.