JPS62103836A - 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 modified silicone oil 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 modified silicone oil 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 modified silicone oil is exemplified by the modified silicone oil expressed by formula. The compounding ratio 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 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 an optical recording medium in which ferromagnetic metal thin films are formed as a magnetic layer on a non-magnetic support, and the ferromagnetic metal thin film serving as the magnetic layer contains perfluoroalkyl carboxylic acid ester and modified silicone. Oil is used as a lubricant to provide good running performance and wear resistance over a wide range of operating temperatures.

This improves durability.

[Conventional technology]

Conventionally, as a magnetic recording medium, r-
FezO=, r-Fez○□ containing Co.

Fe=Oa, Fe=o containing Co, r-Fe2
0. Powdered magnetic materials such as heltolide compounds of I and Fe20a, co-containing bertolide compounds, oxide ferromagnetic powders such as Cr0z, or alloy magnetic powders whose main components are Fe, Co, Ni, etc., are mixed with vinyl chloride-acetic acid. BACKGROUND ART Coated magnetic recording media are widely used, which are manufactured by applying a magnetic paint with a concentration of 11% to an organic binder such as a vinyl copolymer, polyester resin, or polyurethane resin and drying the coating.

In response, with the increasing demand for high-abundance magnetic recording, ferromagnetic metal monolithic materials such as CoNi alloys have been developed using plating and vacuum thin film forming techniques (vacuum evaporation, sputtering, ion blating, etc.). A so-called ferromagnetic metal thin film type magnetic recording medium, which is directly deposited on a non-6ft 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 many advantages, such as extremely small loss of thickness and thickness during reproduction, and there is no need to mix an organic binder, which is a non-magnetic material, into the magnetic layer (the packing density of the n-type material can be increased). ing.

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 intermittent motion with a magnetic head during the recording and reproducing process of magnetic heads, and during this time, the movement 11 must be carried out smoothly and in a stable manner. Must be. Also, 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 coating the magnetic layer of the magnetic recording medium, that is, the surface of the thin ferromagnetic metal, with a lubricant 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. required to do so.

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.

Therefore, the present invention maintains adhesion and lubricity under any operating temperature conditions, and )9! Low friction coefficient and Y' resistance
An object of the present invention is to provide a magnetic recording medium with excellent wear resistance and running properties.

[Means for solving problems]

In order to achieve the above-mentioned object, the present inventors have found that the ester moiety of perfluoroalkylcarboxylic acid contains a long-chain alkyl group, an alkyl group having a double bond, and a branched alkyl group. By combining a perfluoroalkyl carboxylic acid ester incorporating either of the above and modified silicone oil, a lubricating effect with a higher IQ than when used alone is achieved, and at the same time, the operating temperature range is expanded. They discovered that it is possible to do this and completed the present invention, in which a thin ferromagnetic metal film is formed on a non-magnetic support, and a perfluoroalkyl carboxylic acid ester and a perfluoroalkyl carboxylic acid ester are added to the thin ferromagnetic metal film. It is characterized by a lubricant layer containing modified silicone oil.

The perfluorofurkyl 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). 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 it is less than that, the lubricating effect will be insufficient, and on the other hand, if carbon exceeds O for several months, it will solidify in a low temperature range, and therefore the lubricating effect under low temperature conditions will decrease. 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 having a double bond.

On the other hand, the modified silicone oil used in the present invention has a general formula (wherein, at least one of R+ and Rt is an alkyl group having 2 to 10 carbon atoms, or a group having a carboxy group or a methyl ester thereof at its terminal, The remainder is a methyl group.In the formula, m and n represent integers of 1 to 100.

The blending ratio of the above-mentioned perfluoroalkyl carboxylic acid ester and modified silicone oil is 30 =
It is preferable that it is 70-70:30. In addition to the above-mentioned perfluoroalkyl carboxylic acid ester and modified silicone oil, conventionally known lubricants may be used in combination.

A method for attaching a lubricant layer containing these perfluoroalkyl carboxylic acid esters and modified silicone oil to a ferromagnetic metal thin film is to dissolve the above lubricant in a solvent and apply the resulting solution to the surface of the ferromagnetic metal thin film. The ferromagnetic metal thin film may be coated or sprayed, or conversely, the ferromagnetic metal thin film may be immersed in this solution and dried.

Here, the coating layer is 0.5 mg/m ~ low/
d, more preferably 1/m to 20/d. If this coating amount is too small, F
The effects of lowering the J+=coefficient and improving wear resistance and durability are not achieved. 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, which actually worsens 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, and cellulose acetate butyrate, vinyl resins such as polyvinyl chloride 1 polyvinylidene chloride, plastics such as polycarbonate, polyimide, and polyamideimide, aluminum alloys, and titanium. Examples include light metals such as 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, 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 the evaporated metal (ferromagnetic metal material) is deposited on a disk substrate. Generally, in order to obtain a high coercive force, oblique deposition is employed in which the ferromagnetic metal material is deposited diagonally on 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 ion blating 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 10-1 to 10-' Torr, and the ferromagnetic metal material is The process is to evaporate it.

” The above sputtering method uses 1O-1 to l O-'T
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. There is a sputtering method, a magnetron sputtering method using a magnetron radiation 1E 111, and the like.

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

■ etc. bottom t1! ! A film may be formed in advance.

In any of the above methods, the substrate is coated with Bi, Sb, Pb, Sn, Ga, and In.

By first depositing a base metal layer such as CD, Ge, Si, Te, etc., and depositing the film in the direction perpendicular to the substrate surface, it is possible to obtain an in-plane isotropic structure without magnetic anisotropy orientation ( For example, it is suitable for forming a magnetic disk.

The ferromagnetic metal material f-1 used when forming a metal magnetic image using such a vacuum thin film forming technique includes C, in addition to metals such as Fe, Co, and Ni.

-Ni alloy, Co-Pt alloy, Co-Ni-Pt alloy,
Fe-Co alloy, Fe-Ni alloy, Fe-Co-Ni alloy, Fe-C0-B alloy, Co-N1-Fe-B alloy,
Examples include a Co-Cr alloy or one in which metals such as Cr and AI2 are contained. In particular, when a Co--Cr alloy is used, a perpendicularly magnetized film is formed.

Formed by this method (the thickness of the magnetic layer is
It is about 0.04 to 1 μm.

[Effect]

The lubricant layer containing perfluoroalkyl carboxylic acid ester and modified silicone oil firmly adheres to the ferromagnetic metal film, exhibits a good lubrication effect, and reduces the coefficient of friction. In particular, perfluoroalkylcarboxylic acid esters exhibit good lubrication effects even at low temperatures, and modified silicone oils exhibit good lubricity at room temperatures, so 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 I.

Nonadecafluorodecanoic acid isostearyl ester C1
13(CIl□)Il-CI-CIl□-0CO-(C
F2) aCFgo[(C11□)6cHi An ester reaction was carried out between isostearyl alcohol and nonadecafluorodecanoic acid in toluene using p-toluenesulfonic acid as a catalyst. That is, after refluxing for 1 hour, 3
Water in the solvent was removed over time, and toluene was removed under reduced pressure using an evaporator, followed by purification using a vacuum device. (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 140-145°C10, 2 mmtlg. Ta.

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 121O to 1380cm-', an absorption of ester at 1780cm-', and an absorption due to CH stretching vibration at 2910cm-'.In addition, in the mass spectrum by the chemical ion method, the molecular ion beak M “ is seen in 765, so
We decided on this structure.

Synthesis Example 2゜Pentadecafluorodecanoic acid isostearyl ester C
1h(CIl□) a-C1l-CHt-OCO-(C
Fz) acFx(C11□)6CIh By the same method as in the previous synthesis example ■, isostearyl alcohol and pentadecafluorooctanoic acid were added in toluene.
The reaction was carried out using p-toluenesulfonic acid as a catalyst.

bp 120-134℃ (0.2 mml1mm1l
1200-1400cm-'1780cm-'2920cm-' M゛ 665 Synthesis Example 3゜Pentadecafluorooctanoic acid isononyl ester (C
LhC(Ctl□)C11(CH3)CII□CIl□
OCO(CF 2 ) aCF y By the same method 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 mml1 mm1l 12
10-1390cm-'1185cm-'2850-2'960cm-'M" 539 Synthesis Example 4゜Pentadecafluorooctanoic acid sulfyl ester CH3
(CL) * (CI(zcH=cH) 2 (Cll
□), 0CO(CFz) 6CF! 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℃ (0.2mmHg)IRl
210=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 μm.

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 modified silicone oil (weight ratio 1:1) were diluted with a solvent (Freon). The coating amount of the solution was 10nw/
A sample tape was prepared by coating the sample tape so as to have a width of n4 and cutting it into 1/2 inch width.

(Left below) Table 1 In Table 1, dimethylpolysiloxane is KF-96 manufactured by Shin-Etsu Chemical Co., Ltd., and the modified silicone oil is R1・C11HxoCOOH in the general formula of the modified silicone oil.
, R2=CH3, m=20. The value n = 1 was used.

For each sample tape produced, the temperature was 25°C9
The dynamic friction coefficient and shuttle durability were measured under conditions of relative humidity (RH) 50% and -5°C. This coefficient of dynamic friction was determined by applying a constant tension to 5 mm/sec using a guide pin made of stainless steel (StJS 304).
The test was conducted by feeding at a speed of c. 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 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 both room temperature and low temperature conditions, and is extremely stable in running. No damage was observed on the tape surface after this. In addition, the durability was also excellent, and even after 150 shuttle runs, no decrease in output by 13 dB was observed. On the other hand, in the comparative tape without l('BI lubricant layer, the V; It was also bad.

〔Effect of the invention〕

As is clear from the above explanation, in the present invention, perfluoroalkyl carboxylic acid ester and modified silicone oil are used as lubricants for the ferromagnetic metal thin film type magnetic recording medium, so that it can be operated under any temperature conditions. 17 friction coefficient can be reduced, 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 non-magnetic support; and a lubricant layer containing a perfluoroalkyl carboxylic acid ester and modified silicone oil coated on the ferromagnetic metal thin film.