JPS63113820A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve long-period lubricity, running performance and durability by depositing a specific perfluoroalkylthiophenol deriv. on a thin ferromagnetic metallic film formed on a nonmagnetic base. CONSTITUTION:A lubricating agent layer 3 is coated on the surface of the thin ferromagnetic metallic film 2 deposited and formed on the nonmagnetic base 1. This lubricating agent is the perfluoroalkylthiophenol deriv. expressed by the formula. In the formula, R denotes CnF2n+1 or omega-H-CnF2n and (n) is >=2 integer. Such lubricating agent layer 3 adheres well to the thin film 2, exhibits a high lubricating effect over a long period of time even at and under a high temp. and high humidity or at a low temp. and contributes to an improvement of the running durability as well.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention provides a method for forming a ferromagnetic metal thin film as a magnetic layer on a non-n-type support by vacuum thin film forming techniques such as vacuum evaporation and sputtering. This invention relates to a so-called ferromagnetic metal thin film type magnetic recording medium.

[Invention (already required)]

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. ,
,. 1 or ω-H-C,.

represents Fin, where n is an integer and n≧2. ) The present invention aims to provide a magnetic recording medium coated with a perfluoroalkylthiophenol derivative represented by the following formula, which exhibits excellent runnability, abrasion resistance, and durability under a wide range of usage conditions.

[Conventional technology]

Conventionally, as a magnetic recording medium, r-
r F ez O5r containing FezO,, Co
pe 304.7 containing Fex Oa + Co
- Bertolide compound of Fe 103 and Fe, O,
Powder magnetic materials such as ferromagnetic oxide powders such as Co-containing bertolide compounds and Cry, or alloy magnetic powders containing Fe, Co, Ni, etc. as main components are combined with vinyl chloride-vinyl acetate copolymers, polyester resins, etc. , 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 developed using plating and vacuum thin film formation 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-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 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, the surface smoothness of the magnetic layer is extremely good, so the substantial contact area is large, making it easy for adhesion phenomena (so-called sticking) to occur and friction. The coefficient becomes larger, etc.
It has many shortcomings in terms of durability, running performance, etc., and improving them is a major issue.

In general, magnetic recording media are subjected to high-speed relative motion with a magnetic head during the process of recording and reproducing signals, and during this time, the magnetic recording medium must move smoothly and stably. It is better to minimize wear and damage caused by contact with the product.

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 solidify or freeze at low temperatures such as 0 to -5℃, so it is difficult to fully demonstrate their lubricating effect. I couldn't.

Therefore, the present invention provides a lubricant that maintains adhesion and lubricity under a wide range of usage conditions and maintains a lubricating effect over a long period of time, and provides a magnetic recording medium with excellent running performance and durability. With the goal.

[Means for solving problems]

As a result of intensive research to achieve the above object, the present inventors discovered that perfluoroalkylthiophenol derivatives exhibit good lubricating effects over a wide temperature range, leading to the completion of the present invention. The present invention is characterized in that a ferromagnetic metal thin film is formed on a nonmagnetic support, and a lubricant layer containing the perfluoroalkylthiophenol derivative as a main component is adhered to the ferromagnetic metal thin film.

That is, the magnetic recording medium of the present invention, as shown in FIG. 2
) and a lubricant layer (3) containing a perfluoroalkylthiophenol derivative applied to the surface of the lubricant layer (3).

The perfluoroalkylthiophenol derivative used as a lubricant in the present invention has the general formula (wherein R is Cn
Fzn** or (d-H-C, lFm++1,
n is an integer and n≧2. ) is a compound represented by

In the above general formula (1), R in the perfluoroalkylthiophenol derivative is C6F6. , *+ or ωHC
, lFg-+, and the carbon number n is preferably an integer of 2 or more, and the carbon number n of the perfluoroalkyl group
is less than 2, the desired lubrication effect cannot be expected.

The above-mentioned perfluoroalkylthiophenol derivatives are
Reported by Paul L. Coe et al.
alSociety Parkin I) 917
It can be easily synthesized by the method described in 1974.

For example, N.K. Barbou (A, ni, Barbou)
Journal of Chemical Society (Journal of Chemistry) reported by R) et al.
Perfluoro-n-
Propyl (pentafluorophenyl)methanol is synthesized, this alcohol is converted into a ketone using chromium trioxide, and then reduced with sulfur tetrafluoride and a small amount of aluminum fluoride to synthesize perfluorobutylhenzene.

Perfluoroalkylthiophenol can be synthesized by reacting this with sodium hydrosulfide in ethylene glycol-pyridine at 0°C. The reaction formula is as follows.

Of course, it goes without saying that other perfluoroalkylthiophenol derivatives can also be synthesized by the same method.

The perfluoroalkylthiophenol derivative synthesized as described above may be used alone as a lubricant, but it may also be used in combination with a conventionally known lubricant to further expand the usable temperature range. good.

The lubricants used include fatty acids or their metal salts;
Fatty acid amide, fatty acid ester, fatty alcohol or its alkoxide, fatty amine, polyhydric alcohol,
Sorbitan ester, manninotan ester, sulfurized fatty acid, aliphatic mercaptan, modified silicone oil, perfluoroalkyl ethylene oxide, perfluoropolyethers, higher alkyl sulfonic acid or its metal salt, perfluoro alkyl sulfonic acid or its ammonium salt, or Examples include metal salts thereof, perfluoroalkylcarboxylic acids or metal salts thereof.

In particular, perfluoroalkyl carboxylic acid esters and carboxylic acid perfluoroalkyl esters have good low-temperature properties and are therefore suitable for use in combination with the above-mentioned perfluoroalkylthiophenol derivatives.

Furthermore, in order to cope with more severe usage conditions and maintain the lubricating effect, an extreme pressure agent is added to the perfluoroalkylthiophenol derivative at a weight ratio of about 30:0 to 70:30. Good too.

When the extreme pressure agent makes partial metal contact in the boundary lubrication area, it reacts with the metal surface due to the accompanying frictional heat, forming a reaction product film to prevent friction and wear. In particular, phosphorus-based extreme pressure agents such as phosphate esters, phosphite esters or phosphate ester amine salts, sulfur-based extreme pressure agents such as sulfurized oils and fats, monosulfides or polysulfides, iodine compounds, bromine compounds or chlorine compounds, etc. Halogenated extreme pressure agents, organometallic extreme pressure agents such as thiophosphates, thiocarbamates, or metal alkyl dithiocarbamates, and complex extreme pressure agents such as dialkylthiophosphate amines, thiophosphates, or thiophosphites are well known. It is being

Moreover, in addition to the above-mentioned lubricants and extreme pressure agents, a rust preventive agent may be used in combination as required.

As the rust preventive agent that can be used, any rust preventive agent that is normally used as a rust preventive agent for this type of magnetic recording medium may be used, such as dihydric phenol.

Phenols such as alkylphenol or nitrosophenol, naphthols such as pure naphthol or nitro-, nitroso-, amino-, or halogeno-substituted naphthol, methylquinone, hydroxyquinone.

Quinones such as aminoquinone, nitroquinone or halogenoquinone, diarylketones such as hensifhenone and its derivatives hydroxybenzophenone and aminobenzophenone, acridine, 4-quinolitool, heterocyclic compounds containing nitrogen atoms such as kynurenic acid or riboflavin, tocopherol or guanosine, etc. heterocyclic compounds containing an oxygen atom, heterocyclic compounds containing a sulfur atom such as sulfolane, sulfolene or bithione, compounds having a mercapto group such as thiophenol, dithizone or thiooxin, thiocarboxylic acids such as ethanethioic acid or rubeanic acid or their salts , diazosulfide, benzothiazoline, and other thiazole compounds. The above-mentioned rust preventive agent may be used in combination with a lubricant, but for example, as shown in FIG. 2, a ferromagnetic metal thin film (
It is most effective if the rust preventive layer (4) is first applied to the surface of 2), and then the lubricant layer (3) is applied in 2N or more parts.

A method for depositing a lubricant layer containing these perfluoroalkylthiophenol derivatives on a ferromagnetic metal thin film is to apply or spray a solution obtained by dissolving the above lubricant in a solvent onto the surface of the ferromagnetic metal Wi film. Alternatively, the ferromagnetic metal thin film may be immersed in this solution and dried.

Here, the coating amount is 0.5■/d~100■/rr
It is preferably 1/d to 20/d, and more preferably 1/d to 20/d. If the coating amount is too small, the effect of lowering the coefficient of friction and improving wear resistance and durability will not be achieved. On the other hand, if it is too large, 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 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 nonmagnetic support may be in any form such as a film, sheet disk, card, or drum.

The surface roughness of the non-magnetic support may be controlled by forming one or more types of protrusions such as mountain-like protrusions and wrinkle-like protrusions on the surface of the non-magnetic support.

For example, the above-mentioned mountain-like protrusions have a particle size of 5 when forming a polymer film.
It is formed by internally adding inorganic fine particles of about 0.00 to 3000, and the height from the polymer film surface is 100 to 3000.
1000 people, density approximately 1X10' to 10XIO'/2 seals. Calcium carbonate (CaCOs), silica, alumina, etc. are suitable as the inorganic fine particles used to form the mountain-like protrusions.

The wrinkle-like protrusions are undulations formed by applying and drying a dilute solution of resin using a specific mixed solvent, for example, and have a height of 0.01 to 10 μm, preferably 0.01 to 10 μm. 03-0.5μm, the shortest distance between protrusions is 0.1
~20 μm. The resin for forming these wrinkle-like protrusions includes polyesters such as polyethylene terephthalate and polyethylene naphthalate, polyamides,
Single substance, mixture or copolymer of various resins such as polystyrene, polycarbonate, polyacrylate, polysulfone, polyethersulfone, polyvinyl chloride, polyvinylidene chloride, polyvinyl butyral, polyphenylene oxide, phenoxy resin, etc., and contains a soluble solvent. things are suitable. Then, a solvent that is a poor solvent for the resin and has a boiling point higher than the good solvent is added in an amount of 10 to 100 times the amount of the resin to a solution in which these resins are dissolved in the good solvent and the resin concentration is 1 to 11,000 pp. By applying and drying the solution on the surface of a polymer film, a yi layer having very fine wrinkle-like irregularities can be obtained.

The granular protrusions are formed by attaching organic ultrafine particles such as acrylic resin or inorganic fine particles such as silica or metal powder in a spherical or semispherical shape. The height of this granular protrusion is
50-500 people, density 1 x 106 - 50 x 10'' pieces/
The length should be approximately 1m.

The surface properties of the ferromagnetic metal thin film that is the magnetic layer can be controlled by forming at least one type of these protrusions, but the effect is enhanced by combining two or more types. By forming the protrusions and the protrusions, durability and running properties are greatly improved.

In this case, the overall height of the protrusion is 100 to 200
Preferably within the range of 0 people, the density is 1m”
It is preferable that the number is lXl0' to lXl0' on average.

Further, the ferromagnetic metal FiJ film, which 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 one-place method, 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 brating 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 10-3 Torr, and the above-mentioned ferromagnetic metal material is evaporated during the discharge. That is what it is.

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.

When this sputtering method is used, a base film such as Cr or W3 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, or TR, and depositing the film in a direction perpendicular to the substrate surface, excellent in-plane magnetic properties can be achieved 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
t alloy, CoNi-Pt alloy, Fe-Co alloy, Fe-
Examples include Ni alloy, Fe-Go-Ni alloy, Fe-Co-B alloy, Co-N1-Fe-B alloy, C0-Cr alloy, 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 this method is 0.
．． It is about 0.04 to 1 μm.

Moreover, as shown in FIG. 3, I
A so-called bank coat layer (5) may be formed on the side opposite to the side on which the AI magnetic metal thin film (2) and the lubricant layer (3) are provided. The bank coat layer (5) is made of vinyl chloride.
Vinyl acetate, phenolic resin or polyvinyl fluoride, binder resin such as polyurethane resin or butadiene copolymer, and carbon-based fine powder to impart conductivity or added to control surface roughness and improve durability. It is formed by coating the surface of a non-magnetic support with a back coat paint in which a powder component such as an inorganic pigment is mixed and dispersed in an organic solvent such as acetone, methyl ethyl ketone or benzene.

A lubricant may be used in the above-mentioned back coat layer (5). In this case, there is a method of internally adding a lubricant to the above-mentioned balafcoat layer (5), or a method of depositing a lubricant on the back coat layer (5). In any case, the above lubricants include fatty acids, fatty acid esters, fatty acid amides,
Conventionally known lubricants such as metal soap, aliphatic alcohol, paraffin, silicone, etc. can be used. Furthermore, a perfluoroalkylthiophenol derivative may be used as a lubricant for this Banokko-ii(5) as in the above-mentioned Lubricating N(2).

[Effect]

Perfluoroalkylthiophenol m11 exhibits a good lubricating effect over a wide temperature range, so by applying it to a ferromagnetic metal thin film, the coefficient of friction of a ferromagnetic metal thin film type magnetic recording medium can be significantly reduced. be done.

〔Example〕

Hereinafter, specific examples of the present invention will be described, but the present invention is not limited to these examples.

Example 1 CO was deposited on a 14 μm thick polyethylene terephthalate film by oblique vapor deposition to form a ferromagnetic metal thin film with a thickness of 1000 μm.

Next, 2,3,5,6-tetrafluoro-4-heptafluoro-n-propylthi 5
A sample tape was prepared by coating the sample tape at a concentration of mg/% and cutting it into 1/2 inch width.

Example 2 2.3.5. instead of 2.3,5.6-tetrafluoro-4-heptafluoro-rhopropylthiophenol.
6-Tetrafluoro-4-nonafluoro-n-butylthiof A sample tape was prepared in the same manner as in Example 1.

Example 3 2.3,5.6-tetrafluoro-4-heptafluoro-rhopropylthiophenol instead of 2.3,5.6-tetrafluoro-4-heptafluoro-rhopropylthiophenol.
A sample tape was prepared in the same manner as in Example 1 except for 6-tetrafluoro-4-pentadecafluoro-n-octyl.

Example 4 2.3.5.6 instead of 2.3,5.6-tetrafluoro-4-heptafluoro-npropylthiophenol
-tetrafluoro-4-ω-11-decafluoro-n-
A sample tape was prepared in the same manner as in Example 1 except for the pliers.

For each sample tape 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/see under a constant tension. In addition, the shuttle durability was evaluated by running the shuttle for 2 minutes each time and determining the number of shuttles with an output of up to 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 the table below.

(Leaving space below) As is clear from the above table, each of the examples to which the present invention is applied has a small dynamic friction coefficient under each temperature condition, and the running is smooth and stable, and even after 100 reciprocations, the tape No surface damage was observed.

Furthermore, the still 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 lubricant layer, the friction coefficient increased as the number of reciprocating runs increased, running was unstable, tape friction was observed, and durability was poor.

〔Effect of the invention〕

As is clear from the above description, in the present invention,
Since perfluoroalkylthiophenol derivatives are used as lubricants for ferromagnetic metal thin film magnetic recording media, the coefficient of dynamic friction can be reduced under a wide range of temperature conditions, resulting in magnetic recording media with excellent running stability and wear resistance. It can be used as a recording medium.

[Brief explanation of the drawing]

FIG. 1 is an enlarged cross-sectional view of a main part showing an example of a configuration of a magnetic recording medium to which the present invention is applied, and FIG. FIG. 3 is an enlarged sectional view of a main part showing still another example of the configuration of a magnetic recording medium to which the present invention is applied. 1...Nonmagnetic support 2...Ferromagnetic metal thin film 3...Lubricant layer 4...Rust preventive layer 5...Back coat layer

Claims (1)

[Claims] A ferromagnetic metal thin film is formed on a non-magnetic support, and on the ferromagnetic metal thin film there is a general formula ▲a numerical formula, a chemical formula, a table, etc.▼ (However, in the formula, R is C_nF_2_n_+_1 or ω-
A magnetic recording medium coated with a perfluoroalkylthiophenol derivative represented by H-C_nF_2_n, where n is an integer and n≧2.