JPH043326A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve traveling property, durability, storage property, and especially to obtain good coefft. of friction at high temp. and high humidity by incorporating a specified sulfone deriv. into a magnetic layer. CONSTITUTION:A sulfone derv. expressed by formula I is incorporated into the magnetic layer or into the surface of the magnetic layer on a nonmagnetic supporting body. Thereby, traveling property, durability, and storage property can be improved and especially good coefft. of friction is obtained at high temp. and high humidity without an addition of a lubricant and without losing electromagnetic conversion characteristics or head wearing property. In formula, R is hydrocarbon of 10 - 26 carbon number, and R' is hydrocarbon of 1 - 26 carbon number.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention relates to a magnetic recording medium having a magnetic layer on a non-magnetic support, and particularly to a magnetic recording medium that has excellent runnability, durability, and storage stability under a wide range of temperature and humidity conditions. This invention relates to an excellent magnetic recording medium.

[Conventional technology]

In magnetic recording media, there is an increasing demand for higher density recording, and it is known that one way to meet this demand is to make the surface of the magnetic layer smooth.

Furthermore, ferromagnetic thin film magnetic recording media are also being developed as next-generation media.

However, in the above-mentioned media, if the surface of the magnetic layer is smoothed to improve the electromagnetic conversion characteristics, the friction coefficient of the contact between the magnetic layer and the device system increases while the magnetic recording medium is running, and as a result, it becomes difficult to use it for a short period of time. The magnetic layer of the magnetic recording medium tends to be damaged or peeled off.

In order to deal with the second problem, a method is known in which a lubricant is added to the magnetic coating liquid or a method is applied to the surface of the magnetic layer.

Conventional lubricants include mineral oil, silicone oil, higher alcohol, higher fatty acid, fatty acid ester, beef tallow, whale oil,
Animal or vegetable oils have been used.

When the amount of conventional lubricants listed above is small, increasing the amount of lubricant to enhance its lubrication effect weakens the mechanical strength of the magnetic coating, causing the magnetic layer to be scraped and scraped powder to contaminate the running path. Or, sufficient durability for still playback could not be obtained. In order to improve the durability of still playback, it is necessary to
It is known to use a mixture of a fatty acid ester such as butyl stearate and a fatty acid such as myristic acid, as disclosed in No. 1, et al. However, when these disclosed examples are used, there is a drawback that when the tape is run at high temperatures, friction increases and the running tension of the magnetic tape increases.

When fatty acids are used alone, they are effective in improving image quality, but in order to obtain lubricity, it is necessary to use large amounts, and in this case, the magnetic layer becomes soft and its mechanical strength decreases. However, there was a drawback that the durability of still playback deteriorated.

In addition, the combined use of fatty acids and fatty acid ester compounds described in Japanese Patent Publication No. 51-39081 provides good still durability and relatively low tension, but under high temperature conditions such as 85% RH (relative humidity). However, this had the disadvantage that running tension increased.

In order to eliminate these drawbacks, Japanese Patent Application Laid-Open No. 56-80828
The paper proposes the use of saturated or unsaturated fatty acids and aliphatic hydrocarbyl phosphates in the magnetic layer. This proposal states that it has excellent lubricity at room temperature and high temperature, and has good abrasion resistance and durability for still regeneration.

However, recently, as flexible disk drive devices for consumer use such as VTRs, personal computers, and word processors have become popular and have become film-based, the conditions for using magnetic recording media have also changed, such as use at low temperatures or use at high temperatures and high humidity. It has started to spread. Therefore, magnetic recording media must be stable so that their running durability does not change under various expected conditions, but conventionally known lubricants are not sufficient. There was a problem that performance deteriorated.

In addition, as another measure to improve running durability,
A method of adding abrasives (hard particles) to the magnetic layer has been proposed and implemented, but when adding an abrasive to the magnetic layer for the purpose of improving the running durability of the magnetic layer, it is necessary to add a considerable amount of the abrasive. If it is not added to the head, the effect of the addition will not be apparent (that is, it is ultimately difficult to obtain running durability without sacrificing electromagnetic conversion characteristics and head wear resistance.

Therefore, the present inventors conducted intensive studies on a lubricant that would solve the above problems, and found that by retaining 88 sulfone bodies in the magnetic layer, it has excellent durability and environmental adaptability that could never be achieved with conventional lubricants. The inventors have discovered that it is possible to obtain the following, and have come to form the present invention.

(Objective of the Invention) An object of the present invention is to provide a magnetic recording medium which has improved reproduction output, runnability, durability, and storage stability over a wide range of temperature and humidity conditions, and particularly has an improved coefficient of friction at high temperatures.

(Structure of the Invention) That is, the above object of the present invention is to provide a magnetic recording medium having a magnetic layer provided on a non-magnetic support, characterized in that the magnetic layer contains a sulfone derivative represented by the following general formula or on the surface of the magnetic layer. This can be achieved using a magnetic recording medium.

(However, R is a hydrocarbon group having 10 to 26 carbon atoms, and R' is a hydrocarbon group having 1 to 26 carbon atoms.) More preferably, the above object of the present invention is such that the magnetic layer contains a ferromagnetic powder and a binder. , and at least one of the resins contained in the binder has a polar group, and the magnetic layer is a ferromagnetic metal thin film formed by oblique vapor deposition. This can be achieved using a magnetic recording medium.

That is, the present invention provides that by including a sulfone derivative in the magnetic layer or making it exist on the surface of the magnetic layer, stable running durability can be obtained even when used under harsh conditions such as high temperature, low temperature, and low humidity. Moreover, it does not deteriorate when stored.

Although it is not clear why the sulfone derivative of the present invention provides such effects, the following may be considered.

That is, the sulfone group, which is a polar group of the compound of the present invention, has a high affinity for inorganic materials and easily adheres to the surface of a metal material and a binder film. Therefore, hydrophobic hydrocarbon groups are easily oriented on the surface and exhibit good lubrication performance. Furthermore, it has high solubility in solvents such as hexane and MEK, and when top coated, it can be applied uniformly to the surface of the metal material, making it possible to form a uniform alignment film. On the other hand, in the case of sulfonic acid ester, since it is itself a strong acid, it corrodes the surface of metal materials. In addition, in the case of metal salts and ammonium salts of sulfonic acids, the salt dissociates over time and becomes an acid that corrodes the metal material, or it is difficult to coat uniformly due to low solubility in solvents, making it difficult to form a uniform alignment film. I can't do that.

Further, the compound of the present invention exhibits remarkable effects particularly when a polar group-containing binder is used as a binder for a coated magnetic recording medium.

This is because the polar group of the compound of the present invention is easily soluble in the binder and interacts very strongly with the polar group of the binder, so that the lubricating performance can be maintained due to its anchoring effect. On the other hand, sulfonic acid esters are strongly adsorbed to the ferromagnetic powder, so they do not come out to the surface, and it is thought that sulfonic acid ester salts have low solvent solubility and crystals precipitate on the surface, resulting in poor slipperiness.

The sulfone derivatives used in the present invention will be explained in detail below.

(However, R is a hydrocarbon group having 10 to 26 carbon atoms. R' is a hydrocarbon group having 1 to 26 carbon atoms.) As the sulfone derivative of the present invention, R is a sulfone derivative having a hydrocarbon group of 10 to 26 carbon atoms. If so, it can be selected regardless of molecular weight, branched structure, unsaturated bond, and isomer structure, but preferably non-aromatic hydrocarbon groups (however,
Aralkyl groups and the like are included. ), and straight-chain alkyl groups are particularly preferred.

In this case, if the number of carbon atoms is 9 or less or 27 or more, the hydrophobes are too short or too long and difficult to orient, resulting in no lubricity.

Regarding R', if it is a sulfone derivative of 1 to 26 hydrocarbon groups, the molecular weight, branched structure, unsaturated bond,
Although it can be selected regardless of the isomer structure, non-aromatic hydrocarbon groups (however, aralkyl groups and the like are included) are preferred, and straight-chain alkyl groups are particularly preferred. Among these, those having an alkyl group having 1 or more and 4 or less or 10 or more and 26 or less carbon atoms are more preferable from the viewpoint of orienting the hydrophobes in a high degree of orientation.

Further, the total number of carbon atoms is preferably 44 or less.

If it is 44 or more, the solubility in solvents and binders will be poor, and it will precipitate on the surface or even become oriented, making it impossible to exhibit lubricity.

in particular CHsCCHz)□5CHCHs 11\ OCH.

Compound 7 Compound 8 C) 13 0 These compounds can be prepared by dissolving sulfide or sulfoxide in a solvent (acetone, MEK, etc.) and adding an oxidizing agent (hydrogen peroxide, perbenzoic acid, ozone, chromic acid, potassium permanganate, hypochlorite, etc.). Obtained by adding sodium chlorate, nitric acid, dinitrogen tetroxide, sodium metaperiodate, ruthenium oxide, osmium oxide (■), hydroperoxide, etc.), boiling and refluxing for several hours, followed by extraction, distillation under reduced pressure, and recrystallization. I can do it.

When added internally to the magnetic layer of a general coated magnetic recording medium, the appropriate amount is 0.1 to 8% by weight based on the ferromagnetic powder. When applying a top coat to the surface of the magnetic layer of a coated magnetic recording medium, a suitable amount is 2 to 50 .mu./bo.

If the amount used exceeds this range, the sulfone derivative on the surface will be excessive, which may cause problems such as sticking and moisture absorption. On the contrary, there are problems such as decreased durability.

If the amount used is below this range, the surface amount will be insufficient and no effect will be obtained.

In the present invention, other lubricants may be mixed.

Lubricants that can be used in combination include saturated and unsaturated fatty acids (myristic acid, stearic acid, oleic acid, etc.), metal soaps,
N-substituted/N-unsubstituted fatty acid amides, fatty acid esters (fatty acid esters of various monoesters such as sorbitan, glycerin, polyvalent esters, esters of polybasic acids, etc.), ester compounds with ether bonds, higher aliphatic alcohols , monoalkyl phosphates, dialkyl phosphates, trialkyl phosphates, paraffins, silicone oils, animal and vegetable oils, mineral oils, higher aliphatic amines; inorganic fine powders such as graphite, silica, molybdenum disulfide, tungsten disulfide; polyethylene,
Resin fine powder such as polypropylene, polyvinyl chloride, ethylene-vinyl chloride copolymer, polytetrafluoroethylene; α-olefin polymer; unsaturated aliphatic hydrocarbon that is liquid at room temperature, terminal-modified or unmodified perfluoroalkyl poly Examples include ether and fluorocarbons.

The preferable amount of these mixed lubricants to be used varies depending on the mode of use, but it is generally 1/1 of the amount of the sulfone derivative of the present invention.
The amount used is ~2 times as much.

In the present invention, methods for retaining the sulfone derivative in the magnetic layer include a method in which the sulfone derivative is contained in the magnetic layer, a method in which the surface is topcoated (a method in which the material is dissolved in an organic solvent, applied or sprayed on the substrate, and then dried, and a method in which the material is melted and There are two methods: a method in which the material is applied to the substrate by immersing the material in an organic solvent solution, a method in which the material is adsorbed to the surface of the substrate by immersing the material in a solution prepared by dissolving the material in an organic solvent, and a method in which the material is adsorbed onto the surface of the substrate, and a method in which the material is applied by the Langmuir-Prodgett method.

As the ferromagnetic powder used in the present invention, ferromagnetic iron oxide powder, Co-doped ferromagnetic iron oxide powder, ferromagnetic chromium dioxide powder, ferromagnetic metal powder, ferromagnetic alloy powder, barium ferrite, etc. can be used.

Examples of ferromagnetic alloy powder include a metal content of 75-t% or more, a metal content of 80 wt% or more, or at least one ferromagnetic metal or alloy (Fe, Co, Ni, Fe-C).
o, Fe-Ni, Co-Ni.

Co-Fe-Ni), and the metal content is 20wt%
Other components (AI, Si, S, Sc.

Ti V, Cr, Mn, Cu, Zn, Y, Mo.

Rh, Pd, Ag, Sn, Sb, B, Ba, TaW
Re Au, Hg, Pb, P, La,
Ce.

Pr, Nd, Te, Bi, etc.) can be mentioned. Further, the ferromagnetic metal component may contain a small amount of water, hydroxide, or oxide.

Methods for producing these ferromagnetic powders are known, and the ferromagnetic powder used in the present invention can also be produced according to known methods.

The shape and size of the ferromagnetic powder are not particularly limited and can be widely used. The shape may be needle-like, rice-grain-like, spherical, cubic, plate-like, etc., but needle-like and plate-like shapes are preferred from the viewpoint of electromagnetic conversion characteristics. There are no particular restrictions on the crystallite size or non-surface area, but depending on the crystallite size. 400Å or less, 30 on S BET
i/g or more is preferable. The PH1 surface treatment of ferromagnetic powder can be used without particular restrictions (the surface may be treated with a substance containing elements such as titanium, silicon, aluminum, etc., or it can be treated with a substance containing elements such as carboxylic acid, sulfonic acid, sulfuric acid ester, phosphonic acid, phosphoric acid). It may be treated with an organic compound such as an adsorptive compound having a nitrogen-containing heterocycle such as ester or benzotriazole.The preferable pH range is 5 to 10.In the case of ferromagnetic iron oxide fine powder, bivalent The iron/trivalent iron ratio is not particularly limited and can be used.

As the binder used in the present invention, known thermoplastic resins, thermosetting resins, radiation-curable resins, reactive resins, and mixtures thereof, which have been conventionally used as binders for magnetic recording media, can be used. can.

The above resin has a Tg of -40°C to 150°C and a weight average molecular weight of 10,000 to 300,000, preferably 10,000 to 100,000.

Examples of the thermoplastic resin include vinyl chloride/vinyl acetate copolymer, vinyl chloride, vinyl acetate and vinyl alcohol,
Copolymers with maleic acid and/or acrylic acid, vinyl copolymers such as vinyl chloride/vinylidene chloride copolymers, vinyl chloride/acrylonitrile copolymers, ethylene/vinyl acetate copolymers, nitrocellulose, cellulose acetate Propionate, cellulose derivatives such as cellulose acetate butyrate resin, acrylic resin,
Rubber resins such as polyvinyl acetal resin, polyvinyl butyral resin, polyester polyurethane resin, polyether polyurethane, polycarbonate polyurethane resin, polyester resin, polyether resin, polyamide resin, amino resin, styrene butadiene resin, butadiene acrylonitrile resin, silicone resin Examples include resins and fluorine resins.

Among these, vinyl chloride resin is preferred because it has high dispersibility of ferromagnetic fine powder.

The above thermosetting resins or reactive resins are those whose molecular weight becomes extremely large when heated, such as phenol resins, phenoxy resins, epoxy resins, curable polyurethane resins, urea resins, melamine resins, alkyd resins, silicone resins, and acrylic resins. system reaction resin, epoxy-polyamide resin, nitrocellulose melamine resin, mixture of high molecular weight polyester resin and isocyanate prepolymer, urea formaldehyde resin, low molecular weight glycol/
Included are high molecular weight diol/polyisocyanate mixtures, polyamine resins, and mixtures thereof.

The radiation-curable resin used is one in which a group having a carbon-carbon unsaturated bond is bonded to the thermoplastic resin as a radiation-curable functional group. Preferred functional groups include acryloyl and methacryloyl groups.

In the binder molecules listed above, polar groups (epoxy groups, C
Oz M, OH, NRt, NR2X.

sow M, -05Ch M, -PO3M, -0PO
, M□, where M is hydrogen, an alkali metal or ammonium, and when there are multiple M's in one group, they may be different from each other, X represents a halogen ion, R
is hydrogen or an alkyl group) is preferable in view of the dispersibility and durability of the ferromagnetic powder, and the effect of addition of the sulfone derivative of the present invention can be clearly seen. The content of polar groups is in the range of 10-7 to 10-'' equivalents, more preferably in the range of 10-6 to 10-4 equivalents, per gram of polymer.

If the content of polar groups is less than 10 -7 equivalents, the amount of lubricant that interacts with the film will be small, making it difficult to form a uniform alignment film and reducing slipperiness. Moreover, if the amount is more than 10-' equivalent, the viscosity of the binder increases and the dispersibility decreases, which is not preferable.

The polymer binders listed above may be used alone or in combination, and can be cured by adding known incyanate-based binders and/or radiation-curable vinyl monomers.

As an isocyanate-based crosslinking agent, two incyanate groups are used.
A polyisocyanate compound having at least 3 diisocyanates, such as tolylene diisocyanate, 4,4' diphenylmethane diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, naphthylene-1,5-diisocyanate, 0-)luidine diisocyanate, isophorone diisocyanate, triphenyl Examples include isocyanates such as methane diisocyanate, reaction products of these isocyanates and polyalcohols, and polyisocyanates produced by condensation of these isocyanates. These polyisocyanates are manufactured by Nippon Polyurethane Industries ■Karakoro*-to L, Coronet)
HL, Coronate H, Coronate EH, Coronate 2
014, Coronate 2030, Coronate 2031, Coronate) 2036, Coronate) 3015, Coronate 3
040, Coronate 3041, Millionate MR.

Millionate MTL, Daltosec 1350, Daltosec 2170, Daltosec 2280, Shikinichi Pharmaceutical Co., Ltd.
Takenate) D102, Takenate) DIION, Takenate D200, Takenate D202, Resident Bayer ■
From, Sumidur N75, Desmodule from West German Bayer, Desmodule IL, Desmodule N
It is commercially available from Dainippon Ink and Chemicals under trade names such as Burnock D850 and Burnock D802.

Radiation-cured vinyl yarn threads are compounds that can be polymerized by radiation irradiation and have one or more carbon-carbon unsaturated bonds in the molecule, such as (meth)acrylic esters and (meth)acrylamide. Examples include allyl compounds, vinyl ethers, vinyl esters, vinyl heterocyclic compounds, N-vinyl compounds, styrene, (meth)acrylic acid, crotonic acid, itaconic acid, and olefins.

Among these, diethylene glycol di(meth) having two or more (meth)acryloyl groups is preferable.
Acrylate, polyethylene glycol (meth)acrylates such as triethylene glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipenta Examples include erythritol hexa(meth)acrylate, a reaction product of a polyisocyanate and a hydroxy(meth)acrylate compound, and the like.

These crosslinking agents preferably comprise 5 to 45 wt% of the total binder containing crosslinking agents.

All the binders (including crosslinking agents) in the magnetic layer of the present invention
The blending amount is 10 to 40 wt%, preferably 15 to 3 Qwt%, based on the ferromagnetic powder.

If the blending ratio of the binder is greater than the above range, the degree of filling of the ferromagnetic powder will be low and the 71M1 conversion characteristics will be degraded, whereas if it is less, the running durability will be degraded.

As the material of the non-magnetic support, polyesters such as polyethylene terephthalate and polyethylene 2.6 naphthalate; polyolefins such as polyethylene and polypropylene; cellulose derivatives such as cellulose triacerate; resins such as polycarbonate, polyimide, and polyamideimide are used. If necessary, it may be metallized with a metal such as aluminum, or may be a metal foil such as aluminum foil or stainless steel foil.

The support may be in any form such as a tape, disk, film, sheet, card, or drum, and various materials are selected depending on the form.

The thickness of the non-magnetic support is 3 to 100μ, preferably 3 to 20μ for magnetic tape, and 20 to 20μ for magnetic disk.
100μ is a commonly used range.

The magnetic layer of the magnetic recording medium of the present invention preferably further contains inorganic particles having a Mohs hardness of 5 or more as an abrasive.

The inorganic particles used are not particularly limited as long as they have a Mohs hardness of 5 or more. Examples of inorganic particles having a Mohs hardness of 5 or more include AIto3 (Mohs hardness 9), TiO(
5), Tilt (6.5).

5iOz (7), Snow (6.5).

CrzOs (9), and (z Few Os
(5.5), and these can be used alone or in combination.

Inorganic particles with a Mohs hardness of 8 or more are preferred for (. As a result, head clogging is likely to occur, and running durability is also poor.

The content of the inorganic particles is usually in the range of 0.1 to 20 parts by weight, preferably in the range of 1 to 10 parts by weight, based on 100 parts by weight of the ferromagnetic powder.

In addition to the above-mentioned inorganic particles, the magnetic layer preferably contains carbon black (particularly one having an average particle size of 10 to 300 nm (nanometers; 10 -9 m)).

Next, an example of a method for manufacturing the magnetic recording medium of the present invention will be described.

First, a magnetic paint is prepared by mixing and dispersing ferromagnetic powder, a binder, and, if necessary, other fillers and additives in a solvent. As the solvent used during kneading, solvents commonly used for preparing magnetic paints can be used.

There is no particular restriction on the kneading method, and the order of addition of each component can be set as appropriate.

For example, it is also possible to prepare lubricants, additives, and crosslinking agents dissolved in a solvent and add them to a ferromagnetic powder dispersion prepared with a solvent, binder, ferromagnetic powder, etc. immediately before coating. .

When preparing a magnetic paint, known additives such as dispersants, antistatic agents, lubricants, etc. can also be used.

Examples of dispersants include fatty acids having 12 to 22 carbon atoms, salts or esters thereof, compounds in which part or all of the hydrogen atoms of these compounds are replaced with fluorine atoms, amides of the above fatty acids, aliphatic amines, and higher alcohols. , polyalkylene oxide alkyl phosphates, alkyl phosphates, alkyl borates, sarcosinates, alkyl ether esters, trialkyl polyolefins, oxyquaternary ammonium salts and lecithin,
Known dispersants such as low molecular weight epoxy compounds can be used.

When using a dispersant, the ferromagnetic powder 1 usually used is
It is used in a range of 0.1 to 10 parts by weight per 00 parts by weight.

Examples of antistatic agents include conductive fine powders such as carbon black and carbon black graft polymers; natural surfactants such as saponins; nonionic surfactants such as alkylene oxides, glycerins, and glycidols; higher alkyl amines. cationic surfactants such as quaternary ammonium salts, salts of pyridine and other heterocyclic compounds, phosphoniums or sulfoniums;
Anionic surfactants containing acidic groups such as carboxylic acid, phosphoric acid, sulfuric acid ester groups, and phosphoric ester groups; Examples include amphoteric surfactants such as amino acids, aminosulfonic acids, and sulfuric acid or phosphoric esters of amino alcohols. can. When using the above conductive fine powder as an antistatic agent, for example, 0.1 to 1 part by weight per 100 parts by weight of ferromagnetic powder.
It is used in a range of 0 parts by weight, and when a surfactant is used, it is also used in a range of 0.12 to 10 parts by weight.

Note that the above-mentioned additives such as dispersants, antistatic agents, and lubricants are not strictly limited to having only the above-mentioned effects; for example, if the dispersant is a lubricant, Alternatively, it may act as an antistatic agent. Therefore, it goes without saying that the effects of the compounds exemplified by the above classifications are not limited to those listed in the above classifications, and when using a substance that has multiple effects, the amount added should be It is preferable to determine the action and effect using hydrocyanic acid.

The magnetic paint thus prepared is applied onto the non-magnetic support described above. At this time, a plurality of magnetic paints may be applied sequentially or simultaneously in layers.

Coating can be performed directly onto the non-magnetic support, but it can also be applied onto the non-magnetic support via an intermediate layer such as an adhesive layer.

The intermediate layer herein refers to a layer of adhesive alone or a composite film layer formed by dispersing non-magnetic fine particles such as carbon in a binder.

The intermediate layer containing carbon black can be arbitrarily selected as a binder from among various binders used in magnetic layers. The particle size of carbon black is 10 to 50 nm (
The binder: carbon black preferably has a weight ratio of 100:10 to 100:150.The thickness of the intermediate layer is 0.1 to 2 μm in the case of a simple adhesive layer. In the case of a composite layer containing non-magnetic powder, the thickness is preferably 0.5 to 4 μm.

In addition, the intermediate layer contains the same lubricant used for the magnetic layer.
Or a different lubricant may be added.

Details of the method of dispersing the above-mentioned ferromagnetic powder and binder and the method of coating it on a support are described in Japanese Patent Laid-Open Publications No. 54-46011 and No. 54-21805.

The thickness of the magnetic layer thus applied after drying is generally in the range of about 0.5 to 10 μm, usually 0.5 to 10 μm.
It is coated to a thickness of 7 to 6.0 μm.

When a magnetic recording medium is used in the form of a tape, the magnetic layer coated on the non-magnetic support is usually subjected to a treatment for orienting the ferromagnetic powder in the magnetic layer, that is, a magnetic field orientation treatment, and then dried. On the other hand, in the case of a disk-shaped medium, a non-orientation treatment using a magnetic field is applied to remove the magnetic properties. Thereafter, the surface is smoothed if necessary, and then cured by heat curing and/or radiation irradiation if necessary, and then cut into a desired shape.

A known back layer may be provided on the side of the nonmagnetic support on which the magnetic layer is not provided.

In the present invention, oblique deposition is a method in which a vapor flow of a ferromagnetic metal material is made incident at a certain angle of incidence θ relative to the normal to the substrate surface to deposit a magnetic thin film on the substrate surface.

In the present invention, the angle of incidence is generally 45° to 90°.
It is desirable that the angle of incidence θmax is 60° to 90°, and the angle of incidence θmin is preferably 45″ to 75°.

As the ferromagnetic metal thin film material used in the present invention, Fe
, Co, Ni, or other metals, or Fe-Co, Fe-N
i, Co-Ni, Fe-Co-Ni, Fe-Rh, Fe
-Cu, Co-Cu, C.

-Au, Co-Y, Co-La5 Co-Pr, Co-
Cd, Co-3m5 Co-Pt, Ni-Cu.

Mn-B i, Mn-5b, Mn-Aj2, Fe-C
, Co-Cr, Ni-Cr, Fe-Co-Cr, Ni-
It is a ferromagnetic alloy such as Co-Cr or Fe-Co-Ni-Cr. Particularly preferred is 75% by weight of CO or Co.
It is an alloy that contains

The total thickness of the laminated ferromagnetic metal thin film is generally about 0.02μ because it needs to be thick enough to provide sufficient output as a magnetic recording medium and thin enough to perform high-density recording.
m to 5.0 μm, preferably 0.05 μm to 2.0
It is μm. The thickness of each magnetic thin film may be designed to be equal, or the thickness may be ±50% of the thickness of the ferromagnetic metal thin film closest to the substrate.

The vapor deposition in the present invention refers to the above-mentioned US Pat. No. 334,263.
In addition to the usual vacuum deposition described in the specification etc. of No. 2,
It also includes a method of forming a ferromagnetic metal thin film on a supporting substrate in an atmosphere in which the vaporized molecules have a large mean free path by ionizing or accelerating a vapor flow using an electric field, magnetic field, electron beam irradiation, etc. , for example, JP-A-5L-14
Field vapor deposition method as shown in specification No. 900B, Japanese Patent Publication No. 43-11525, Japanese Patent Publication No. 46-20484,
Special Publication No. 47-26579, Special Publication No. 4945439,
Ionization vapor deposition methods such as those disclosed in JP-A-49-33890, JP-A-49-34483, and JP-A-49-54235 can also be used in the present invention.

Substrates used in the ferromagnetic metal thin film of the present invention include polyethylene terephthalate, polyimide, polyamide, polyvinyl chloride, cellulose triacetate, polycarbonate,
Plastic bases such as polyethylene naphthalate are preferred. In particular, in the present invention, the above-mentioned flexible plastic base having a surface roughness (ra) of 0.012 μm or less is preferable. Here, the surface roughness (ra) is JI
With the centerline average roughness shown in item 5 of SBO601,
The cutoff is 0.25 kaku. Furthermore, an undercoat layer may be provided on the plastic base, and the surface roughness (ra) of the undercoat layer may be set to 0.012 μm or less, and this may be used as the substrate.

Furthermore, in the present invention, a nonmagnetic layer may be interposed between the laminated ferromagnetic metal thin films, and preferred materials for the nonmagnetic intermediate layer are Cr, Si, and AN.

Mn, Bi, Ti, Sn, Pb, In, Zn, Cu
Alternatively, it is a layer composed of these oxides or nitrides.

(Effects of the Invention) By containing a sulfone derivative in the magnetic layer or on the surface of the magnetic layer, the sulfone moiety is easily adsorbed to the binder or the surface of the metal thin film, and the hydrophobic chains are arranged on the outside and easily aligned. Therefore, it exhibits excellent and stable lubrication properties without increasing the friction coefficient at high temperatures or low temperatures and low humidity.In addition, magnetic recording media with a magnetic layer made of a thin metal film are susceptible to rust, and there is a problem that sulfonic acid and Although strong acids and salts or esters of strong acids, such as esters of sulfonic acids, promote rust, the sulfone derivatives of the present invention cause very little corrosion of metals.

[Example] Next, the present invention will be specifically explained using Examples, but the present invention is not limited thereto.

Note that "parts" in the examples indicate "parts by weight."

[Example 1] After cross-dispersing the following composition for 48 hours using a kneader and a ball mill, 5 parts of polyisocyanate was added thereto, and after cross-dispersing for another hour, it was cross-dispersed using a filter having an average pore size of 1 μm. The mixture was filtered and a magnetic paint was prepared. The obtained magnetic paint was applied onto the surface of a polyethylene terephthalate support having a thickness of 10 μm using a reverse roll so that the thickness after drying was 4.0 μm.

Magnetic paint composition Ferromagnetic alloy powder (&l composition: Fe94%, Zn.

4%, Ni2%; anti-magnetic crab 15000e; specific surface area 54
Bo/g) 100 parts vinyl chloride/vinyl acetate/maleic anhydride copolymer (400X110A manufactured by Nippon Zeon ■).

Polymerization degree 400) (A) or vinyl chloride/vinyl acetate copolymer (polymerization degree 400)
(B) 12 parts polyester polyurethane (weight average molecular weight 40,000, number average molecular weight 25,000, type and number of polar groups are listed in Table 1) (C) 5 parts coronate, 4 parts abrasive ( α-Alumina, average particle size 0.3 μm) 5 parts Lubricant (1st notation if) 1 part oleic acid 1 part butyl stearate 2 parts carbon black (average particle size 40 nm) 300 parts methyl ethyl ketone The non-magnetic support coated with the paint is subjected to field orientation using a 3000 Gauss magnet while the magnetic paint is not dry.
After further drying, the film was subjected to supercalender treatment and slit into 1-width pieces the next day to produce an 811Il videotape. (Samples Nα1 to 23) [Example 2] A cobalt-nickel magnetic film (film thickness: 150 nm) was obliquely deposited on a 13 μm thick polyethylene terephthalate film to prepare a raw material for a magnetic recording medium. An electron beam evaporation source was used as the evaporation source, and it was charged with a cobalt-nickel alloy (Co: 80 wt%, Ni: 20%), and the incident angle was 50 degrees in an oxygen stream in a vacuum of 5 x 10-' Torr. Oblique evaporation was performed so that Various materials dissolved in methyl ethyl ketone were coated on the magnetic metal thin film of the obtained magnetic recording medium, and samples were prepared by drying and designated as sample magnets 24 to 39 (Table 2).

The videotape obtained as above was recorded at 7MH using a VTR (Fuji Photo Film ■: FUJ 1X-8).
The signal of z was recorded and played back. The relative playback output of the videotape was measured when the 7 MHz playback output recorded on the reference tape (sample size 18) was set as OdB.

50g of the obtained videotape and stainless steel pole (
7) With tension (TI) in contact (wrap angle 180'), under these conditions, the videotape is 3. 3CIll/S
The l force (T, ) required to run the vehicle at a speed of was measured. Based on this measured value, the friction coefficient μ of the videotape was determined using the following calculation formula.

(Listed in Tables 1 and 2) μ=1/π・1n (T!/TI) The friction coefficient test was a, 5℃, 10%RH, b,
The test was carried out under two conditions: 45° C. and 90% RH.

In addition, in order to investigate the corrosion of the ferromagnetic powder on the tape, the tape was left in a thermostat for a week at temperatures ranging from 20°C to 40°C and humidity from 10% to 100%, and then observed under a microscope to check the state of rust on the sample floor. A relative comparison was made of the amount of mackerel using 33 as lOO.

As is clear from the results in Table 1, samples 11m1 to 14.16 and sample floors 24 to 32 using sulfone derivatives of the present invention were all tested at low temperatures, low humidity, and high temperatures.
It can be seen that the friction coefficient is low under both conditions, and the tape does not corrode.

On the other hand, without using the compound of the present invention, we simply used fatty acids (sample N1118.34) and esters (sample N[Li2
．． When only 35) is used, the reproduction output is low and the coefficient of friction is large, especially at high temperatures (condition b), and sulfonic acid (sample series 36 to 38) causes problems such as large corrosion of the tape. It turns out that there are many things.

Claims (3)

[Claims] (1) A magnetic recording medium comprising a magnetic layer provided on a non-magnetic support, characterized in that a sulfone derivative represented by the following general formula is contained in the magnetic layer or on the surface of the magnetic layer. (General formula) ▲ Numerical formulas, chemical formulas, tables, etc. are available ▼ (However, R is a hydrocarbon group with 10 to 26 carbon atoms R' indicates a hydrocarbon group with 1 to 26 carbon atoms.) (2) The magnetic layer includes a ferromagnetic powder and a binder, and at least one resin contained in the binder has a polar group. magnetic recording media. (3) The magnetic recording medium according to claim (1), wherein the magnetic layer is a ferromagnetic metal thin film formed by oblique deposition.