JPS62117130A - 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 heterocyclic compd. contg. an oxygen atom 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 a heterocyclic compd. contg. an oxygen atom is coated on the ferromagnetic metallic 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 perfluo roalkylcarboxylic acid with the corresponding alcohol. Tocopherol, etc., can be exemplified as the heterocyclic compd. contg. an oxygen atom and used as a rust preventive agent. The compounding ratio by weight of the perfluoroalkylcarboxylic acid ester to the heterocyclic compd. contg. an oxygen from 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 vacuum thin film forming techniques such as vacuum deposition and 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 perfluoroalkyl carboxylic acid ester and a heterocyclic compound containing an oxygen atom are used in the ferromagnetic metal thin film as the magnetic layer. The objective is to improve running performance, abrasion resistance, durability, and corrosion resistance by applying a protective layer containing 3i as the main component.

[Conventional technology]

Conventionally, as a magnetic recording medium, r
T −F e t containing F e 1031 CO
O1+Fes Oa, Fe containing Co, Oi+r
- Bertolide compound of FezO3 and F (330a,
Powder magnetic materials such as ferromagnetic oxide powders such as Co-containing bertolide compounds and Crux, or alloy magnetic powders containing Fe, Co, Ni, etc. as main components are combined with vinyl chloride-vinyl acetate copolymers, polyester resins, Applying magnetic paint dispersed in an organic binder such as polyurethane resin.
Coated magnetic recording media, which are produced by drying, are widely used.

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 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 the substantial contact area becoming larger, the a-sticking phenomenon (so-called sticking) becoming more likely to occur, and the coefficient of friction becoming larger, and improvement of these problems has become a major issue. In general, a magnetic recording medium is subjected to high-speed relative motion between the magnetic field and the magnetic field during the recording and reproducing process of magnetic signals, and during this time, the medium must travel smoothly and stably. 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 Y4 film type magnetic recording medium has many problems in practical properties such as running performance, IT durability, and corrosion resistance. Improvements are being attempted.

However, these conventional attempts are still far from satisfactory.For example, the operating temperature range of conventionally widely used lubricants is limited, especially at low temperatures such as 0 to -5℃. There is a problem in that many of them are solid or frozen, and their lubricating effect cannot be fully 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.

[Means for solving problems]

As a result of intensive research to achieve the above-mentioned object, the present inventors have found that perfluoroalkylcarboxylic acid esters exhibit excellent lubricating effects over a wide temperature range, and that heterocyclic compounds containing nitrogen atoms We have completed the present invention by discovering that these compounds are effective in improving corrosion resistance, and that practical properties can be synergistically improved by combining them. That is, the present invention forms a ferromagnetic metal thin film on a nonmagnetic support, and coats the ferromagnetic metal thin film with a protective layer mainly composed of a perfluoroalkyl carboxylic acid ester and a heterocyclic compound containing an oxygen atom. 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, 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 divided alkyl group, or an alkylene chain having a double bond.

On the other hand, examples of the oxygen atom-containing heterocyclic compound used as a rust preventive in the present invention include tocopherol, morin, quercetin, and ascorbic acid.

1,8-naphthalic anhydride, resorufin, kojic acid.

Examples include dehydroacetic acid, oxazole, 3-aminophthalimide, 4-aminophthalimide, uridine, thymidine, guanosine, isatoic anhydride, and the like.

The blending ratio of the above-mentioned perfluoroalkyl carboxylic acid ester and the heterocyclic compound containing an oxygen atom is preferably 10:2 to io:1o in terms of weight ratio. In addition to the heterocyclic compound containing an oxygen atom, conventionally known lubricants and rust preventives may be used in combination.

A method for attaching these perfluoroalkyl carboxylic acid esters and rust inhibitors (heterocyclic compounds containing oxygen atoms) to a ferromagnetic metal thin film is to dissolve the perfluoroalkyl carboxylic acid esters and rust inhibitors in a solvent. The ferromagnetic metal thin film may be coated or sprayed on 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 coating amount is 0.5■/ff1-100■/
d is preferable, and more preferably 1 .mu./rrl to 20 .mu./M. 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 sticking phenomenon occurs between the sliding member and the ferromagnetic metal FI film, and the running performance becomes worse.

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, aluminum alloys, Examples include 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'' to 10-' Torr, and the evaporated metal (ferromagnetic metal material) is deposited on a disk substrate. Generally, in order to obtain a high coercive force, an oblique evaporation method is used in which the above-mentioned ferromagnetic metal material is deposited diagonally on the substrate.Alternatively, to obtain a higher coercive force, the ferromagnetic metal material is deposited in an oxygen atmosphere. It also includes those in which the above vapor deposition is performed.

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 10-4 to 1 O-'' Torr, and the above-mentioned ferromagnetic metal material is heated during the discharge. It is evaporated.

The above sputtering method uses 10-3 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 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, St, TA, 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, C.

-Ni alloy, Co-pt gold alloy Co-Ni-Pt alloy,
Fe-Co alloy, Fs-Ni alloy, Fe-Co-Ni alloy, Fe-Co2B alloy, GO-JJr-Fe-B alloy, Co-Cr alloy or these with Cr, Aj! Examples include those containing metals such as. In particular, Co-C
When r-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 a perfluoroalkyl carboxylic acid ester and a heterocyclic compound containing an oxygen atom, firmly adheres to the ferromagnetic metal thin film, exhibits a good lubricating effect, reduces the coefficient of friction, and Prevents rust from forming on metal film. 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(CHz) a-C)I-CHz-OCO(CFz
). CFff (CH *CH* Isostearyl alcohol and nonadecafluorodecanoic acid were subjected to an ester reaction in toluene using p-toluenesulfonic acid as a catalyst. That is, after heating under reflux for 1 hour,
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℃ 10.2 mmHg Met.

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 1210 to 1380 cm-', an ester absorption at 1780 cm-', and an absorption due to CH stretching vibration at 2910 cn+-'.In addition, in the mass spectrum by the chemical ion method, the molecular ion peak M ' was found in 765, so this structure was determined.

Synthesis Example 2゜Pentadecafluorodecanoic acid isostearyl ester C
Hs (C1h) *-CH-C1b-OCO(CFt
) 6CF3(CHI), CH3 By the same method as in Synthesis Example 1 above, isostearyl alcohol and pentadecafluorooctanoic acid were added in toluene.
p-+-luenesulfone M! The reaction was carried out as a medium.

bp 120-134℃ (0.2mmHg) IR1
200-1400cm-'1780cm-'2920cm-'M" 665 Synthesis Example 3゜Pentadecafluorooctanoic acid isononyl ester (C
) [3) 3C (Co Cl1 (CHI) CIl□CHz
OCO(CFt)acFz 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℃ ('0.2 llmHg) IR121
0-1390cm+-'1785cm-'2850-2960cwa-'M" 539 Synthesis Example 4゜Pentadecafluorooctanoic acid sulfur ester CHs
(CHz)i(CHxCH-CM)t(CHt)sOc
o(CFx)icF3 By 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℃ (0,2a+mHg)TR
1210~1380cm+-'1780cm+-'2850-3020cm-'M''
An AI magnetic metal 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=11) was coated at a coating amount of 10 mg/nf, and the sample tape was cut into a 1x2 inch width.

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

After being left under 80% RH for one week, the coercive force (Hcz) and saturation magnetization (1st) 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 - (HcI - Hct) /Hc+ X
1.00('1) Rate of change of Is"" (Is+ l5
z) / ls+

Next, for each sample tape produced, a temperature of 25
The dynamic friction coefficient and shear durability were measured under the following conditions: °C, relative humidity (R) () 50%, and -5 °C. This coefficient of dynamic friction was determined by using a guide bottle made of stainless steel (SUS304) and applying a constant tension to 5 m1I7.
The test was carried out by sending the sample at a speed of 1.5 seconds. 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 tape of the comparative example without a protective layer, the coefficient of friction increased as the number of reciprocating runs increased, the running was unstable, wear of the tape was observed, and the durability was poor.

〔Effect of the invention〕

As is clear from the above explanation, in the present invention, a perfluoroalkylcarboxylic acid ester and a heterocyclic compound containing an oxygen atom are used as the protective layer of a ferromagnetic metal thin film type magnetic recording medium, so that practical characteristics are achieved. Significant improvements can be made, and a magnetic recording medium with excellent running stability, wear resistance, and corrosion resistance can be obtained.

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] A ferromagnetic metal thin film is formed on a nonmagnetic support, and a protective layer containing a perfluoroalkyl carboxylic acid ester and a heterocyclic compound containing an oxygen atom as a main component is applied to the ferromagnetic metal thin film. magnetic recording medium.