JPS62172527A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a magnetic recording medium having good running property, wear resistance and durability by forming a thin ferromagnetic metallic film on a nonmagnetic substrate and laminating a rust preventive agent layer essentially consisting of heterocyclic compd. contg. S and lubricating agent contg. a perfluoroalkyl carboxylate thereon. CONSTITUTION:The thin film 2 is formed on the nonmagnetic substrate 1 by dispersing ferromagnetic metallic powder into an org. binder, coating the dispersion on the substrate and drying the coating. A sulfolane, rhodanine, etc., are coated as the rust preventive agent 3 thereon. The perfluoroalkyl carboxylate expressed by CnFmCOOCaXb is further superposed as the lubricating agent 4 thereon. In the formula, X is H, F or both thereof and n>=6, m<=2n+1, a>=8, b<=2n+1, CaXb is a straight chain alkyl group of 18<a or aliphat. hydrocarbon group having double bonds or branch of a>18, for which a nonadecafluorodecanoic acid isostearyl ester, etc., are used. The coated amt. of the layers 3, 4 is made about 1-20mg/m<2>. The agents used for the conventional recording media may be used in combination for the layers 3, 4.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention provides a method for forming a ferromagnetic metal f'i 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 thin film type magnetic recording medium in which a film is formed as a magnetic layer.

[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. By applying a rust agent layer and a lubricant layer containing perfluoroalkyl carboxylic acid ester in this order, it has excellent running properties under all usage conditions.

The object is to provide a magnetic recording medium that exhibits wear resistance, durability, and good corrosion resistance.

[Conventional technology]

Conventionally, as a magnetic recording medium, r
Fe, 02. γ-FezO3+”e containing Co
Soa, Fe containing Co) Qa, r - Fe
chlorinated powder magnetic materials such as ferrolide compounds of tc) + and Fe20a, ferromagnetic compounds containing Co, oxide ferromagnetic powders such as CrO□, or alloy magnetic powders mainly composed of Fe, Co, Ni, etc. Painted magnetic recording media are widely used, which are manufactured by applying and drying a sweetened magnetic paint dispersed in an organic binder such as a vinyl-vinyl acetate copolymer, polyester resin, or polyurethane resin.

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 W1115! Type magnetic recording media not only have excellent coercive force and squareness ratio, and excellent electromagnetic conversion characteristics at short wavelengths, but also allow the thickness of the magnetic layer to be extremely thin, making it possible to reduce the thickness during recording demagnetization and reproduction. It has many advantages, such as extremely low loss 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.

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 effective contact area is large (as a result, adhesion phenomenon (so-called sticking) easily occurs. or the coefficient of friction increases, etc.
It has many shortcomings in terms of durability, running performance, etc., and improving them is a major issue.

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

Alternatively, in ferromagnetic metal thin film type magnetic recording media, the magnetic layer is composed of a metal material, so during storage, especially when exposed to high temperature and high humidity, the surface of the magnetic layer tends to corrode. Therefore, there were problems such as the saturation magnetization amount, coercive force, etc. being deteriorated orally.

[Problem that the invention seeks to solve]

As described above, the above-mentioned ferromagnetic metal thin film type magnetic recording media has 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.
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 lubricity over a wide temperature range, and that heterocyclic compounds containing sulfur atoms It is effective in improving corrosion resistance, and furthermore, when a rust preventive layer is first deposited on a ferromagnetic metal thin film and a lubricant layer is deposited on top of that, the rust preventive layer and lubricant layer are They discovered that the method works effectively and completed the present invention.

That is, the magnetic recording medium of the present invention includes a ferromagnetic metal thin film formed on a non-magnetic support, and a rust preventive layer mainly composed of a heterocyclic compound containing a sulfur atom and a perfluorinated metal thin film formed on the ferromagnetic metal thin film. It is characterized in that lubricant layers containing alkyl carboxylic acid esters are deposited in this order.

In the magnetic recording medium of the present invention, the perfluoroalkyl carboxylic acid ester used as the lubricating component of the lubricant layer has the general formula % (1) (where X is a hydrogen atom, a fluorine atom, or both). (n≧6, m≦2n+1., a≧8, b≦23+1).

This perfluoroalkylcarboxylic acid ester is obtained by esterifying a perfluoroalkylcarboxylic acid that is solid at room temperature, lowering the melting point and adding the effect of an alcohol moiety, thereby extending the lubricating effect to a low temperature range.

In the above general formula (1), the aliphatic hydrocarbon group represented by CaXb preferably has a carbon number a of 8 or more,
When the carbon number a is less than 8, lubricity is insufficient. In practice, the above purpose is achieved by using a linear alkyl group with less than 18 carbon atoms, or an aliphatic hydrocarbon group with a double bond or with different techniques if the number of carbon atoms is more than 18. We were able to. Furthermore, the aliphatic hydrocarbon group is
It may be a fluorine-containing aliphatic hydrocarbon group, therefore, in the formula, X may be not only a hydrogen atom but also a fluorine atom, or both a hydrogen atom and a fluorine atom.

On the other hand, the carbon number n of the perfluoroalkyl carboxylic acid moiety is preferably 6 or more. If the carbon number n is less than 6, the lubricity will be insufficient.

However, if the carbon number n is too large, it will solidify in a low temperature range, so in practice it is preferable to keep n≦10.

The above-mentioned perfluoroalkyl carboxylic acid ester is a perfluorocarboxylic acid represented by the general formula % (in the formula, n is an integer of 6 or more, and m is an integer of 2n+1 or less). Formula C, Xb
O11...-(Ill) (In the formula, X is a hydrogen atom, a fluorine atom, or both, a is an integer of 8 or more, and b is an integer of 2a+1 or less.) The following is a reaction formula that can be synthesized by reacting in molar amounts.

C-P-COOH+ CaXbOH--c,
p,cooc,x,--tt+formula complete In the recording medium of the present invention, the above-mentioned perfluoroalkylcarboxylic acid ester may be used alone as a lubricant, but it may be used in combination with a conventionally known lubricant. In addition, the temperature range of use may be expanded.

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, mannisotane ester, sulfurized fatty acid, aliphatic mercaptan, modified silicone oil, perfluoroalkyl ethylene oxide, perfluoropolyethers, higher alkyl sulfonic acid or its metal salt, perfluoroalkyl sulfonic acid or its ammonium salt, or Examples thereof include metal salts thereof, perfluoroalkylcarboxylic acids or metal salts thereof, and the like.

Furthermore, in order to cope with more severe usage conditions and maintain the lubricating effect, the weight ratio is 30:0 to 70:30.
An extreme pressure agent may be used in combination at a certain mixing ratio.

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. Among these, phosphorus-based extreme pressure agents, sulfur-based extreme pressure agents, halogen-based extreme pressure agents, organic metal-based extreme pressure agents, composite type extreme pressure agents, etc. are known.

Specifically, the phosphorus-based extreme pressure agents include tributyl phosphate, trioctyl phosphate, tri-2-ethylhexyl phosphate, trilauryl phosphate, trioleyl phosphate, dibutyl phosphate, dioctyl phosphate, and di-2-ethyl phosphate. xyl phosphate, dilauryl phosphate, dioleyl phosphate-1 phosphate ester, tributyl phosphite, trioctyl phosphite, tri-2-ethylhexyl phosphite, trilauryl phosphite, trioleylphosphite, dibutyl phosphite, Phosphite esters such as dioctyl phosphite, di-2-ethylhexyl phosphite, dilauryl phosphite, dioleyl phosphite, and dibutyl phosphate butylamine salts.

Dibutyl phosphate octylamine salt, dibutyl phosphate stearylamine salt, dioctyl phosphate butylamine salt, dioctyl phosphate octylamine salt, dioctyl phosphate laurylamine salt, dioctyl phosphate stearylamine salt, di-2-ethylhexylphosphate butylamine salt, di-2-ethylhexyl Phosphate octylamine salt, di-2-ethylhexylphosphate laurylamine salt, di-2-
Ethylhexylphosphate stearylamine salt, dilaurylphosphate butylamine salt.

dilauryl phosphate octylamine salt, dilauryl phosphate traurylamine salt, dilauryl phosphate stearylamine salt, dioleyl phosphate butylamine salt, dioleyl phosphate octylamine salt,
Examples include phosphate ester amine salts such as dioleyl phosphate lauryl amine salt and dioleyl phosphate stearyl amine salt.

The above-mentioned sulfur-based extreme pressure agents include mineral oils with unsaturated bonds such as sulfurized whale oil and sulfurized dipentene, sulfurized oils and fats produced by adding sulfur to fats and oils and fatty acids, and heating them, dibenzyl disulfide, and disulfide. diphenyl, di-t disulfide
-Butyl, di-disulfide 5ec-Butyl, di-n disulfide
- disulfides such as butyl, di-t-octyl disulfide, diethyl disulfide, benzyl sulfide, diphenyl sulfide,
Monosulfides such as cyhinyl sulfide, dimethyl sulfide, diethyl sulfide, di-1-butyl sulfide, di-5ec-butyl sulfide, di-n-butyl sulfide, dimethyl trisulfide, di-t-butyl trisulfide, polysulfide di- Examples include polysulfides such as nonyl and olefin polysulfides, thiocarbonates represented by the general formula % (in which R represents a hydrocarbon group), elemental sulfur, and the like.

The halogen-based extreme pressure agent is allyl bromide.

Bromine compounds such as occudecyl bromide, cyclohexyl bromide, stearyl bromide, benzyl bromide, iodine compounds such as benzyl iodide, allyl iodide, butyl iodide, octadecyl iodide, cyclohexyl iodide, hexachloroethane, monochloroethane.

Examples include chlorine compounds such as chlorinated paraffin, chlorinated diphenyl, chlorinated fats and oils, methyl trichlorostearate, pentachloropentadienoic acid, esters of hexachloronaphthenic acid compounds, and imide derivatives of hexachloronaphthenic acid compounds.

Examples of the organometallic extreme pressure agents include zinc diisobutyldithiophosphate, zinc isobutylpentyldithiophosphate, isopropyl-1-methylbutyldithiophosphate, zinc isobutylnonylphenyldithiophosphate, isobutylheptylphenyldithiophosphate, diheptylphenyldithiophosphate, Zinc nonylphenyl dithiophosphate, thiophosphates such as molybdenum dithiophosphate, zinc dimethyldithiocarbamate, zinc diethyldithiocarbamate, zinc dibutyldithiocarbamate, zinc ethylphenyldithiocarbamate, zinc dihendyldithiorubamate, zinc dimethyldithiocarbamate, dimethyldithiocarbamic acid Examples include copper, thiocarbamates such as iron dimethyldithiocarbamate, selenium diethyldithiocarbamate, and silver diethyldithiocarbamate, and metal alkyldithiocarbamates such as molybdenum and antimony.

Examples of the composite extreme pressure agent include dialkylthiophosphate amines such as di-2-ethylhexylthiophosphate amine, propyl chloride, propyl bromide,
In addition to phosphoric acid esters of alkyl halides represented by propyl iodide phosphate, butyl chloride phosphate, butyl bromide phosphate, butyl iodide phosphate, etc., chloronaphsasanthate, etc., the general formula SR (However, in each general formula R represents a hydrogen atom or an alkyl group, an alkenyl group, or an aryl group) Thiophosphates represented by the general formula (wherein R represents a hydrogen atom or an alkyl group, an alkenyl group, or an aryl group) thiophosphate) [etc. are highly effective.

The above-mentioned extreme pressure agents may be used alone, but it is also possible to use a mixture of two or more types.

On the other hand, in the magnetic recording medium of the present invention, the sulfur atom-containing heterocyclic compound used as the rust preventive agent in the rust preventive layer is very effective in improving the corrosion resistance of the ferromagnetic metal thin film. Coupled with the lubricating action of the lubricant containing the alkyl carboxylic acid ester, the durability of the magnetic recording medium can be improved.

Examples of usable heterocyclic compounds containing a sulfur atom include sulfolane, 3-hydroxysulfolane, 3-methylsulfolane, sulfolene, 3-hydroxysulfolene, 3-methylsulfolene, rhodanine, 3-aminorhodanine,
Thiazoline-4-carboxylic acid, 4H-1,4-thiazine, biotin, 3゜6-thioxanthine diamine, 3.6
-thioxanthin diamine-10,10-dioxide and the like.

The above-mentioned heterocyclic compound containing a sulfur atom may be used alone as a rust preventive agent, or may be used in combination with a conventionally known rust preventive agent. Usable rust preventives include any that are normally used as rust preventive agents for this type of magnetic recording media (for example, phenols, naphthols, quinones, diaryl ketones, etc.). Examples include a heterocyclic compound containing a nitrogen atom, a heterocyclic compound containing an oxygen atom, a compound having a mercapto group, a thiocarboxylic acid or a salt thereof, a thiazole compound, and the like.

In the magnetic recording medium of the present invention, as shown in FIG. 1, a ferromagnetic metal thin film (2) is formed on a nonmagnetic support (1), and the surface of this ferromagnetic metal thin film (2) is first coated with the sulfur sulfur. After applying the rust preventive agent 11 (3) whose main component is a heterocyclic compound containing atoms, a lubricant layer (4) containing the perfluoroalkyl carboxylic acid ester is applied thereon. When the rust preventive agent (3) and the lubricant layer (4) are applied separately in 2N or more, a more excellent effect is exhibited than when a mixture of these is applied.

When coating in 21W in this way, the amount of the rust preventive layer (3) or the lubricant layer (4) to be applied is as follows:
It is preferably 0.5μ/d to 100μ/d, and more preferably 1μ/d to 20mg/n. If the coating amount is too small, the corrosion resistance improvement effect or friction The effect of reducing the coefficient and improving wear resistance, runnability, and durability is insufficient, and on the other hand, if it is too much, a sticking phenomenon occurs between the sliding member and the ferromagnetic metal thin film, and the runnability worsens.

As for the coating method, do you use the above-mentioned sulfur-containing heterocyclic compound or perfluoroalkyl carboxylic acid ester as a vehicle? It may be applied using conventional application means such as dissolved 2K, loaf record, spray coating, spin cord, and dipping.

A magnetic recording medium to which the present invention is applied has a non-magnetic support (1
) as a magnetic layer on top! ! A magnetic metal thin film (2) is provided, and the materials for the non-magnetic support (1) include polyesters such as polyethylene terephthalate, polyolefins such as polyethylene and polypropylene, cellulose triacetate, cellulose diacetate,
Examples include cellulose derivatives such as cellulose acetate butyrate, vinyl resins such as polyvinyl chloride and polyvinylidene chloride, plastics such as polycarbonate, polyimide, and polyamideimide, light metals such as aluminum alloys and titanium alloys, and ceramics such as alumina glass. The nonmagnetic support (1) may be in the form of a film, sheet, disk, or card.

Any drum or the like may be used.

The surface roughness of the non-magnetic support (1) may be controlled by forming one or more types of protrusions such as mountain-like protrusions or wrinkle-like protrusions on the surface of the non-magnetic support (1).

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 I X 10'~10XIO
' piece/1IIt. Calcium carbonate (CaC
Suitable materials include Os), silica, and alumina.

The wrinkle-like protrusions are undulations formed by applying and drying a dilute solution of resin using a specific mixed solvent, for example, and the height thereof is 0.01' to 10 pm, preferably 0.03 to 0. .5 μm, the shortest distance between protrusions is 0.1-2
It is set to 0 μm. Examples of the resin for forming the wrinkled protrusions include saturated polyesters such as polyethylene terephthalate, polyethylene naphcrate, polyamide, polystyrene, polycarbonate, polyacrylate, polysulfone, polyethersulfone, polyvinyl chloride, polyvinylidene chloride, Single resins such as polyvinyl butyral, polyphenylene oxide, phenoxy resin,
Mixtures or copolymers with soluble solvents 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 1000 ρρm. The solution was
By applying it to the surface of a polymer film and drying it, a thin layer with extremely 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 1XIO'~50X10'' pieces/
It should be about '+n'.

At least one type of these protrusions is attached to a non-magnetic support (1).
If formed on the base film with ridges, the surface properties of the ferromagnetic metal thin film (2), which is the magnetic layer, can be controlled, but the effect is enhanced by combining two or more types. By forming protrusions and bulge-like protrusions, durability and running properties are greatly improved.

In this case, the overall height of the protrusion is 100 to 200
The density is preferably within the range of 0 people, and the density is law
``It is preferable that the average number per unit is IXLO' to IXIG'.

Further, the ferromagnetic metal material (2), which is the magnetic layer, is formed as a continuous Vt film by a vacuum flj4 film forming technique such as a vacuum evaporation method, an ion blasting method, or a sputtering method.

In the vacuum evaporation method, a ferromagnetic metal material is evaporated under a vacuum of 10-4 to 10-' Torr by resistance heating, high-frequency heating, electron beam heating, etc., 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 evaporation method, in which DC glow discharge and RF glow discharge are caused in an inert gas atmosphere of 10-' to 1 O-Torr, and the above-mentioned ferromagnetic metal material is evaporated during the discharge. It is to let them do so.

The above sputtering method involves causing glow discharge in an atmosphere mainly composed of argon gas at 104 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 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, Go, Si, T1, etc., and depositing the film in a direction perpendicular to the substrate surface, it is possible to achieve excellent in-plane isotropy without magnetic anisotropy orientation. It is possible to form a magnetic layer, and is suitable for use in, for example, magnetic disks.

When forming the ferromagnetic metal Tit film (2) using such vacuum thin film formation technology, the ferromagnetic metal materials used include metals such as Fe, Co, and Ni, as well as Go-Ni alloy and Co. -Pt alloy, Co-N1-pt gold alloy Fe-C
o alloy, Fe-Ni alloy, Fe-Co-Ni alloy, Fe
-Co-B alloy, G.

-Ni-Fe-B alloy, Co-Cr alloy, or these with Cr, An! Examples include those containing metals such as. In particular, when a Go-Cr alloy is used, a perpendicularly magnetized film is formed.

The thickness of the magnetic layer formed is approximately 0.04 to 1 μm.

Furthermore, as shown in FIG. 2, a so-called back coat N (5) may be formed on the surface of the non-magnetic support (1) opposite to the surface on which the ferromagnetic metal thin film (2) is provided. good. Back coat N (5) contains a binder resin and a powder component.
It is formed by applying a bank coating paint mixed and dispersed in a solvent to the surface of the non-magnetic support (1).

Examples of binder resins used in bank coating paints include vinyl chloride-vinyl acetate copolymers, vinyl chloride-vinylidene chloride copolymers, vinyl chloride-acrylonitrile copolymers, and acrylic ester-acrylonitrile copolymers. copolymer, thermoplastic polyurethane elastomer, polyvinyl fluoride, vinylidene chloride-acrylonitrile copolymer, butadiene-acrylonitrile copolymer,
Synthetic rubber resins such as polyamide resins, polyvinyl butyral, cellulose derivatives, polyester resins, and polybutadiene, phenolic resins, epoxy resins, polyurethane curable resins, melamine resins, alkyd resins, silicone resins, acrylic reaction resins, epoxy-polyamide resins, Nitrocellulose-melamine resins, mixtures of high molecular weight polyester resins and isocyanate prepolymers, mixtures of meccrylate copolymers and diisocyanate prepolymers, mixtures of polyester polyols and polyisocyanates, urea formaldehyde resins, low molecular weight glycols /high molecular weight diol/triphenylmethane triisocyanate mixture, polyamine resin, and mixtures thereof.

Alternatively, a binder resin having a hydrophilic polar group may be used to improve the dispersibility of the powder component.

Specifically, SOJ, 0SOJ, -COOM, -
(OM')* (wherein M represents a hydrogen atom or an alkali metal, and Mo represents a hydrogen atom, an alkali metal or a hydrocarbon group), a polyurethane resin or polyester into which a hydrophilic polar group is introduced. Resins, vinyl chloride-vinyl acetate copolymers, vinylidene chloride copolymers, acrylic ester copolymers, butadiene copolymers, etc. can be used.

Various methods can be considered for introducing the above hydrophilic polar group depending on the type of resin, but for example, the following method can be used to introduce the above hydrophilic polar group into polyurethane resin or polyester resin. good.

(1) A method in which the hydrophilic polar group is introduced in advance into a dibasic acid or polyol, which is a raw material for polyurethane or polyester.

(2) A method in which an OH group is left at the terminal or side chain, and this OH group is modified with a compound having a hydrophilic polar group.

In the case of method (2), a compound containing a hydrophilic polar group and a halogen (e.g. chlorine) in the molecule and a polyfunctional polyol as raw materials are used, and OH is added to the terminal or side chain of the polymer chain. The polyurethane resin or polyester resin in which the groups remain are dissolved in a solvent such as dimethylformamide or dimethyl sulfoxide in which both components are soluble, and amines such as pyridine, picoline, triethylamine, or epoxy compounds such as ethylene oxide or propylene oxide are added. OH in the presence of a dehydrochlorination agent such as
A method of introducing a hydrophilic polar group through a dehydrochlorination reaction between the group and chlorine.

+21-2 A compound containing a hydrophilic polar group and an OH group in the molecule,
A method of reacting a polyurethane resin or a polyester resin in which an OH group remains at the end or side chain of a polymer chain via a diisocyanate compound.

There is.

In order to introduce a hydrophilic polar group into the copolymer-based binder resin, (3) a method of using a compound having a hydrophilic polar group and a copolymerizable double bond as a copolymerizable monomer.

(4) As a copolymerizable monomer, use a compound having active hydrogen and a copolymerizable double bond, introduce the above active hydrogen into the side chain of the copolymer, and combine it with a hydrophilic polar group and the above active hydrogen. A method of modification with a compound having a reactive group.

(5) As a copolymerization monomer, use a compound having a group that can react with active hydrogen and a double bond that can be copolymerized, and introduce the group that can react with active hydrogen into the side chain of the copolymer. , a method of modifying with a hydrophilic polar group and a compound having the above-mentioned active hydrogen.

etc.

On the other hand, the above-mentioned powder component includes carbon-based fine powder for imparting conductivity (for example, furnace carbon, channel carbon, acetylene carbon, thermal carbon 9 lamp carbon, etc., among which furnace carbon and thermal carbon are used). ), inorganic pigments (αF e OOH+ αF e z O3 added to control surface roughness and improve durability)
1Cr t 031 T iOz + Z n O+
S i O+SiO□, Sing・2HzO, Ah(
h・2SiOz・2Hz0, 3Mg0・4SiOi
・HgO, AgcOz ・Mg(OR) z ・3Hz
O+A1zO*+CaC01+MgC01,5bzOz
etc.).

Furthermore, as the organic solvent for the above-mentioned back coat paint,
Ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, methyl acetate,
Ethyl acetate, butyl acetate.

Ester solvents such as ethyl lactate and glycol monoethyl acetate, glycol ether solvents such as glycol dimethyl ether, glycol monoethyl ether, and dioxane, aromatic hydrocarbon solvents such as benzene, toluene, and xylene, and fats such as hexane and heptane. Group hydrocarbon solvents, methylene chloride, ethylene chloride,
Carbon tetrachloride, chloroform, ethylene chloride F IJ
General-purpose solvents such as chlorobenzene, chlorinated hydrocarbon solvents such as dichlorobenzene, etc. Constitutional regulations may be used.

A lubricant may be used in combination with the back coat layer (5). In this case, a lubricant may be added internally to the bank coat layer (5), or a lubricant may be added to the bank coat layer (5). There is a method of applying the agent. In any case, the above lubricants include fatty acids, fatty acid esters, fatty acid amides,
Conventional lubricants such as metal soaps, aliphatic alcohols, paraffins, silicones, etc. can be used.

Examples of these lubricants include fatty acids such as saturated fatty acids having 12 or more carbon atoms or unsaturated fatty acids such as lauric acid, myristic acid, palmitic acid, stearic acid, behenic acid, oleic acid, linoleic acid, and lylunic acid. Fatty acids can be used.

As the fatty acid ester, ethyl stearate, butyl stearate, amyl stearate, stearic acid monoglyceride, oleic acid monoglyceride, etc. can be used.

Examples of fatty acid amides include caproic acid amide, capric acid amide, lauric acid amide, palmitic acid amide, stearic acid amide, hehenic acid amide, oleic acid amide,
linoleic acid amide, methylene bisstearic acid amide,
Ethylene bisstearamide, etc. can be used.

As the metal soap, the aforementioned fatty acids Zn, Pb+N
Salts with 1tCo, Fe, ^l, Mg, Sr, Cu, etc., or lauryl sulfonic acid, palmitylsulfonic acid, myristylsulfonic acid, stearylsulfonic acid,
Salts of sulfonic acids such as behenylsulfonic acid, oleylsulfonic acid, linolesulfonic acid, and linolesulfonic acid with the above metals can be used.

As the aliphatic alcohol, cetyl alcohol, stearyl alcohol, etc. can be used.

Saturated hydrocarbons such as n-nonadecane, n-tridecane, and n-tocosan can be used as the paraffin.

As silicones, polysiloxanes in which hydrogen is partially substituted with alkyl groups or phenyl groups, and those modified with fatty acids, aliphatic alcohols, fatty acid amides, etc. can be used.

Furthermore, a lubricant containing a perfluoroalkyl carboxylic acid ester similar to the above lubricant N(4) may be used.

[Effect]

The rust preventive layer, which is mainly composed of a heterocyclic compound containing sulfur atoms, and the lubricant layer, which contains perfluoroalkyl carboxylic acid ester, firmly adhere to the ferromagnetic metal thin film, exhibiting a good lubricating effect and reducing friction. This reduces the coefficient and prevents rust from occurring in ferromagnetic metal thin films. 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.

First, various perfluoroalkyl carboxylic acid esters were synthesized using the following synthesis examples.

Synthesis Example 1゜Nonadecafluorodecanoic acid isostearyl ester CH
s (CHx) a-Cll-CJ-OCO(CFz)
acFs■ (CHt) hcH! An ester reaction was carried out between isostearyl alcohol and nonadecafluorodecanoic acid in toluene using 11-)luenesulfonic acid as a catalyst. That is, after heating under reflux for 1 hour, water in the solvent was removed over 3 hours, toluene was further 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 of the obtained fraction, p, is 140 ~ bQ, 'l mm11g
Met.

In addition, the product can be confirmed by infrared spectroscopy (IR).

Nuclear magnetic resonance analysis (NMR) was performed by quantitative analysis (MASS). As a result, 1210~1380c+s-'
The absorption characteristic of the CF bond is observed at 1780 cm-', the absorption due to the stretching vibration of CH is observed at 2910 cm-', and the molecular ion peak M0 is observed at 765 in the mass spectrum by the chemical ion method. We decided on this structure.

Synthesis Example 2゜Pentadecafluorooctanoic acid isostearyl ester CH3(C1h)a-C11-CHt2-OCO(CF
,)6CF2(C11□)6CH2 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-)luenesulfonic acid as a catalyst.

b, p, 120-134℃ (0.2mmHg
) IR1200~1 400cm-'1780c++-'2920cm-'M" 665 Synthesis Example 3゜Pentadecafluorooctanoic acid isononyl ester (C
11□)zc(C)1t)C11(CH2)C1lzC
HzOCO(CF2)bchBy the same method as in Synthesis Example 1 above, isononyl alcohol and pentadecafluorooctanoic acid were mixed in toluene and p-toluenesulfone M
The reaction was carried out as a medium.

b, p, 94℃ (0.2 mml1 mm1l
1210-1390c#l-'1785c 2850-2960cm-'M" 539 Synthesis Example 4゜Pentadecafluorooctanoic acid sulfuryl ester CH3
(CHt)i(C)IzCH=CH)z(C1lz)s
Oco(CFx)acFsBy 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.

b, p, 135-139℃ (0.2mn+Hg)
IR1210"1380cm-'1780c+s-'2850-3020c11-'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, a solution of the rust preventive shown in Table 1 diluted with a solvent (acetone: ethyl ether = 171) is applied in an amount of 1O+sg/n? It was applied and dried. Furthermore, a perfluoroalkyl carboxylic acid ester (synthesized in the previous synthesis example) shown in Table 1 was applied to the rust preventive layer as a solvent (acetone: ethyl ether-1
A sample tape was prepared by applying the solution diluted in step 1) at a coating amount of 10 μ/d, and after drying, cutting it into 1/2 inch width.

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

After being left under 80% RH for one week, the coercive force (Hcz) and saturation magnetization Jit (Is,) were measured, and the rate of change thereof was determined according to the following formula. As a comparative example, the rate of change was also investigated for a blank tape to which no rust preventive was applied.

The results are shown in Table 2. .

Rate of change in Hc = (Hct lIc+)/Hc+ X1
00(χ)・(21 Change rate of Is - (1st Is
+)/Is+ Occurred.

Next, for each sample tape produced, a temperature of 25
The dynamic friction coefficient and shuttle durability were measured under the following conditions: 50% relative humidity (RH), and -5°C. This dynamic friction coefficient was determined by applying a constant tension to 5 mm/sec using a guide bottle made of stainless steel (SUS304).
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. 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 tape of the comparative example without a lubricant 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, the surface of the ferromagnetic metal thin film, which is the magnetic layer, contains a rust preventive layer mainly composed of a heterocyclic compound containing sulfur atoms and a perfluoroalkyl carboxylic acid ester. Since the lubricant layer is divided into two layers, the anti-corrosion or lubricant effect of each layer is more effectively exhibited, making it possible to significantly improve the practical characteristics and improve running performance. A magnetic recording medium with excellent 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.

[Brief explanation of drawings]

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

Claims (1)

[Claims] A ferromagnetic metal thin film is formed on a non-magnetic support, and a rust preventive layer containing a sulfur atom-containing heterocyclic compound as a main component and a lubricant layer containing a perfluoroalkyl carboxylic acid ester are formed on the ferromagnetic metal thin film. A magnetic recording medium characterized in that the following are deposited in this order.