JP2601364B2 - Magnetic recording media - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a magnetic recording medium comprising a non-magnetic support and a magnetic layer.

[Conventional technology]

Magnetic recording media are widely used as recording tapes, video tapes, floppy disks, and the like.
A magnetic recording medium is basically formed by laminating a magnetic layer in which ferromagnetic powder is dispersed in a binder on a non-magnetic support.

Basically, a magnetic recording medium is required to be at a high level in various characteristics such as electromagnetic conversion characteristics, running durability and running performance. In particular, with the recent popularization of 8-mm video tape recorders and the like, video tapes have high electromagnetic output characteristics, such as high video output and excellent original image reproduction capability. Has been requested.

In magnetic recording media, the demand for higher-density recording is increasing, and it is known that the surface of a magnetic layer is smoothed as one means for improving electromagnetic conversion characteristics.

Ferromagnetic thin film type magnetic recording media have also been developed as next-generation media.

However, in the above 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 during the running of the magnetic recording medium, resulting in short-term use. The magnetic layer of the magnetic recording medium tends to be damaged or the magnetic layer tends to peel off.

To cope with such a problem, a method of adding a lubricant to a magnetic coating liquid or a method of applying a lubricant to the surface of a magnetic layer is known.

Conventionally, mineral oils, silicone oils, higher alcohols, higher fatty acids, fatty acid esters, animal oils such as tallow, whale oil, and shark oils and vegetable oils have been used as lubricants.

When the amount of the conventional lubricant shown above is small, increasing the amount of the lubricant in order to enhance the lubricating effect, the mechanical strength of the magnetic coating film is weakened, the magnetic layer is shaved, and the shaving powder contaminates the traveling path, or is insufficient. The durability of the still reproduction was not obtained. As disclosed in JP-B-28-28367 and JP-B-51-39081, a mixture of a fatty acid ester such as butyl stearate and a fatty acid such as myristic acid is used to improve the durability of still reproduction. It is known. However, when these disclosed examples are used, there is a disadvantage that when running in a high humidity state, the 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, they need to be used in large amounts, in which case the plasticizing effect softens the magnetic layer, There is a disadvantage that the strength is reduced and the durability of the still reproduction is deteriorated.

Hydroxamic acid derivatives have been used as dispersants for magnetic coatings as disclosed in JP-A-1-236425.

Certainly, the addition of the hydroxamic acid derivative slightly improved the dispersibility and still durability, but did not reduce the frictional force.

The combined use of a fatty acid and a fatty acid ester compound described in JP-B-51-39081 results in good still durability and relatively low tension, but 85%.
Under high humidity conditions such as RH (relative humidity), there is a disadvantage that the running tension becomes large.

To solve these drawbacks, Japanese Patent Application Laid-Open No. 56-80828 proposes to use a saturated or unsaturated fatty acid and an aliphatic hydrocarbyl phosphate in the magnetic layer. This proposal describes that it has excellent lubricity at normal temperature and high humidity, and has good abrasion resistance and durability of still reproduction.

However, with the recent popularization and generalization of flexible disk drive devices for consumer use such as those for VTRs, personal computers, and word processors, the use conditions of magnetic recording media have been widespread, such as use under low temperatures or under high temperature and high humidity. It has become. Therefore, the magnetic recording medium must be stable so that its running durability does not fluctuate even under various anticipated conditions. However, a conventionally known lubricant is not sufficient and the performance is not sufficient. There was a problem of deterioration.

As another measure for improving running durability, a method of adding an abrasive (hard particles) to the magnetic layer has been proposed and implemented. However, in order to improve the running durability of the magnetic layer, a method of adding an abrasive (hard particles) has been proposed. When the abrasive is added to the steel, the effect of adding the abrasive is hard to appear unless the abrasive is added in a considerable amount. That is, it is ultimately difficult to obtain running durability without sacrificing the electromagnetic conversion characteristics and head wear.

Accordingly, the present inventors have conducted intensive studies on a lubricant that solves the above-mentioned problems of the magnetic powder coating type, and as a result, the conventional lubricant could not be achieved at all by holding the iron salt of the hydroxamic acid derivative in the magnetic layer. The present inventors have found that excellent durability and environmental adaptability can be obtained, and have accomplished the present invention.

(Object of the Invention) An object of the present invention is to provide a magnetic recording medium which is excellent in electromagnetic conversion characteristics and can always obtain stable running durability even under severe conditions such as high temperature, high humidity and low temperature and low humidity.

(Constitution of the Invention) That is, an object of the present invention is to provide a non-magnetic support and a magnetic recording medium having a magnetic layer provided on the support, wherein the magnetic layer holds an iron salt of a hydroxamic acid derivative represented by the following general formula: This can be achieved by a magnetic recording medium.

However, R is a hydrocarbon group having 10 or more and 26 or less carbon atoms. N is an integer of 1 to 3. More preferably, the object of the present invention is to provide a magnetic recording system in which a magnetic layer comprising a ferromagnetic powder and a binder is provided on a nonmagnetic support. In the medium, at least one resin of the resin occupying 5 wt% or more of the total resin of the binder is an epoxy group, COOM,
At least one polar group of SO ₃ M, OSO ₃ M, PO ₃ M ₂ , OPO ₃ M ₂ (where M is hydrogen, alkali metal or substituted,
Unsubstituted ammonium, and more than one M
May be different from each other), and the magnetic layer contains an iron salt of a hydroxamic acid derivative represented by the general formula, or 10 ^-6 to 10 ^-4 equivalents per gram of the resin. This can be achieved by a magnetic recording medium characterized by holding.

That is, when the magnetic layer contains an iron salt of a hydroxamic acid derivative or is present on the surface of the magnetic layer, the running durability is stable even when used under severe conditions such as high temperature, high humidity, and low temperature and low humidity. The properties are obtained and are not deteriorated by the preservation of the properties. It is not completely clear why such an effect is obtained, but the following may be considered.

Since the iron salt of the hydroxamic acid derivative of the present invention is a cation part and an iron ion, it does not adsorb to the ferromagnetic powder, and also has an anion part, hydroxamic acid, stably present on the surface by interacting with a binder. It is considered that since it is easy to orientate, there is a remarkable effect on the slipperiness.

On the other hand, hydroxamic acid itself does not exist on the surface because it strongly adsorbs to the ferromagnetic powder.

That is, when the hydroxamic acid derivative is used in the magnetic layer, it is first adsorbed on the ferromagnetic powder, so that the hydroxamic acid derivative is present on the surface of the magnetic layer and hardly acts as a lubricant, but in the case of the present invention,
Since the hydroxamic acid derivative is already in the form of an iron salt, it does not easily adsorb to the ferromagnetic powder and easily appears on the surface of the magnetic layer. In addition, since the polar member has interaction with the binder on the surface of the magnetic layer, the hydrophobic hydrocarbon group is easily oriented outward, so that it is considered that the binder exhibits excellent lubricating properties.

The iron salt of the hydroxamic acid derivative of the present invention may have carbon atoms
Any iron salt of a hydroxamic acid derivative having a number of 10 or more and 26 or less can be selected regardless of the molecular weight, branched structure, unsaturated bond, and isomer structure. Specific examples include the following compounds.

Among them, those in which the hydrocarbon group has a linear structure are preferred.

These compounds are, for example, fatty acid hydroxyamides,
It can be obtained by dissolving an ester of sulfonylhydroxyamide, hydrocarbylsulfuric acid hydroxyamide in a solvent (alcohol, chloroform, etc.), and mixing and dissolving iron carbonyl in a solvent (MEK, benzene).

When used in a magnetic layer of a usual coating type magnetic recording medium, the amount is suitably 0.1 to 8% by weight based on the ferromagnetic powder. When the surface of the magnetic layer of the coating type magnetic recording medium is top-coated, ² to 50 mg / m ² is appropriate.

If the amount used exceeds this range, the iron salt of the hydroxamic acid derivative on the surface of the magnetic layer becomes excessive, which may cause a failure such as sticking and moisture absorption. However, there is a problem that the durability is rather lowered due to the action of plasticizing the binder.

If the amount is less than this range, the surface area of the magnetic layer is naturally insufficient and the effect cannot be obtained.

In the present invention, as a method for retaining the iron salt of the hydroxamic acid derivative in the magnetic layer, a method of including the magnetic layer in the magnetic layer and a method of applying a top coat on the surface (a method in which the material is dissolved in an organic solvent and applied to a substrate or sprayed and then dried) A method in which the material is melted and applied to the substrate, a method in which the substrate is immersed in a solution in which the material is dissolved in an organic solvent, and the material is adsorbed on the surface of the substrate, a method based on the Langmuir-Projet method, and the like.

In the present invention, other lubricants may be mixed.

Lubricants that can be used in combination include saturated and unsaturated fatty acid (myristic acid, stearic acid, oleic acid, etc.) metal soaps, N-substituted / N-unsubstituted fatty acid amides, fatty acid esters (various monoesters, sorbitan, glycerin, etc.). Fatty acid esters of polyvalent esters, esterified products of polybasic acids, etc.), ester compounds having an ether bond, higher aliphatic alcohols, monoalkyl phosphates, dialkyl phosphates, trialkyl phosphates, paraffins, silicone oils, animal and vegetable oils, Mineral oil, higher aliphatic amines; inorganic fine powders such as graphite, silica, morphene disulfide, and tungsten disulfide; resin fine powders such as polyethylene, polypropylene, polyvinyl chloride, ethylene-vinyl chloride copolymer, and polytetrafluoroethylene; α-olefin weight Things; normal temperature of liquid unsaturated aliphatic hydrocarbons, terminal modified or unmodified perfluoroalkyl polyethers, fluorocarbons, and the like.

The preferred amount of these mixed lubricants varies depending on the mode of use, but is generally about 1/10 to 2 times the amount of the iron salt of the hydroxamic acid derivative of the present invention.

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 and the like can be used.

Examples of the ferromagnetic alloy powder include a metal content of 75 wt% or more and a metal content of 80 wt% or more of at least one type of ferromagnetic metal or alloy (Fe, Co, Ni, Fe-Co, Fe-Ni, Co- Ni, Co−
Fe-Ni, etc., and other components (Al, Si, S, Sc, Ti, V, Cr, Mn, Cu, Zn, Y, Mo, Rh, Pd, Ag, Sn, Sb,
B, Ba, Ta, W, Re, Au, Hg, Pb, P, La, Ce, Pr, Nd, Te, Bi, etc.). Further, the ferromagnetic metal component may contain a small amount of water or hydroxide.

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

The shape and size of the ferromagnetic powder can be widely used without any particular limitation. The shape may be any of a needle shape, a rice grain shape, a spherical shape, a cubic shape, a plate shape, and the like, and may be a needle shape, a plate shape, and the like. The crystallite size and non-surface area are also not particularly limited, but the crystallite size is 40
0 ° or less, preferably 30 m ² / g or more in SBET. P of ferromagnetic powder
H, The surface treatment can be used without any particular limitation (the surface treatment may be performed using a substance containing an element such as titanium, silicon, or aluminum, or a carboxylic acid, a sulfonic acid, a sulfate, a phosphonate, a phosphate, a benzoate, It may be treated with an organic compound such as an adsorptive compound having a nitrogen-containing heterocycle such as triazole, etc. A preferable pH range is 5 to 10.
It is. In the case of ferromagnetic iron oxide powder, it can be used without any particular limitation on the ratio of divalent iron / 3-valent iron.

The binder used in the present invention may be a known thermoplastic resin, a thermosetting resin, a radiation-curable resin, a reactive resin, or a mixture thereof, which is conventionally used as a binder for a magnetic recording medium. it can.

The 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, a copolymer of vinyl acetate and vinyl alcohol, maleic acid and / or acrylic acid, a vinyl chloride / vinylidene chloride copolymer, a vinyl chloride / vinyl chloride copolymer. Acrylonitrile copolymer, vinyl copolymer such as ethylene-vinyl acetate copolymer, nitrocellulose, cellulose acetate propionate, cellulose derivative such as cellulose acetate butylate resin, acrylic resin, polyvinyl acetal resin, polyvinyl butyral resin, Polyester polyurethane resin, polyether polyurethane, polycarbonate polyurethane resin, polyester resin, polyether resin, polyamide resin,
Rubber-based resins such as amino resins, styrene-butadiene resins, butadiene-agrylonitrile resins, silicone-based resins,
Fluorinated resins can be mentioned.

Among these, a vinyl chloride resin is preferable because of its high dispersibility of the ferromagnetic fine powder.

The thermosetting resin or the reactive resin whose molecular weight becomes extremely large by heating, for example, phenol resin, phenoxy resin, epoxy resin, curable polyurethane resin, urea resin, melamine resin, alkyd resin, silicone resin, acrylic resin -Based reaction resins, epoxy-polyamide resins, nitrocellulose melanin resins, mixtures of high molecular weight polyester resins and isocyanate prepolymers, urea formaldehyde resins, low molecular weight glycol / high molecular weight diol / polyisocyanate mixtures, polyamine resins, and the like. Mixtures.

As the radiation-curable resin, a resin obtained by bonding a group having a carbon-carbon unsaturated bond as a radiation-curable functional group to the thermoplastic resin is used. Preferred functional groups include an acryloyl group and a methacryloyl group.

In the binder molecules listed above, a polar group (epoxy group, CO2
₂ M, OH, NR ₂ , NR 3X, SO ₃ M, OSO ₃ M, PO ₃ M ₂ , OPO ₃ M ₂ , where M is hydrogen, alkali metal or ammonium, and a plurality of Ms in one group In some cases, they may be different from each other. X is a halogen ion. (R is hydrogen or an alkyl group) is preferable in terms of dispersibility and durability of the ferromagnetic powder, and the effect of adding the iron salt of the hydroxamic acid derivative of the present invention is remarkably exhibited. The content of the polar group is preferably from 10 ^-7 to 10 ^-3 equivalents per gram of the polymer,
Further, 10 ^-6 to 10 ^-4 equivalent is a preferable range.

The polymer binders listed above are used alone or in a mixture of several kinds, and can be cured by adding a known isocyanate-based crosslinking agent and / or a radiation-curable vinyl-based monomer.

Two isocyanate groups as an isocyanate-based crosslinking agent
Polyisocyanate compounds having at least one polyisocyanate such as tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, naphthylene-1,5-diisocyanate, o-toluidine diisocyanate, isophorone diisocyanate, triphenylmethane diisocyanate, etc. Isocyanates, reaction products of these isocyanates with polyalcohols, and polyisocyanates formed by condensation of these isocyanates. These polyisocyanates are available from Nippon Polyurethane Industry Co., Ltd. as Coronate L, Coronate HL, Coronate H, Coronate EH, Coronate 2014,
Coronate 2030, Coronate 2031, Coronate 2036, Coronate 3015, Coronate 3040, Coronate 3041, Millinate MR, Millinate MTL, Daltsec 1350, Daltsec 2170, Daltsec 2280, Takenate D102, Takenate D110N, Takenate D20 from Takeda Pharmaceutical Co., Ltd.
0, Takenate D202, Sumitomo Bayer Co., Ltd., Sumidur N75, West German Bayer Co., Ltd. Death Module L, Death Module N, Jis Module HL, and Dainippon Ink and Chemicals, Inc., Burnock D850, Burnock D802, etc. It is commercially available at

The radiation-curable vinyl monomer is a compound polymerizable by irradiation with radiation, a compound having at least one carbon-carbon unsaturated bond in a molecule, and (meth) acrylic esters, (meth) acrylamides Allylic compounds, vinyl ethers, vinyl esters, vinyl heterocyclic compounds, N-vinyl compounds, styrene, (meth) acrylic acid, crotonic acid, itaconic acid, olefins and the like. Of these, preferred are polyethylene glycol (meth) acrylates such as diethylene glycol di (meth) acrylate and triethylene glycol di (meth) acrylate having two or more (meth) acryloyl groups, and trimethylolpropane tri (meta). A) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol penta (meth) acrylate, dipentaerythritol hexa (meth) acrylate, and a reaction product of a polyisocyanate and a hydroxy (meth) acrylate compound.

These crosslinking agents preferably comprise from 5 to 45% by weight of the total binder including the crosslinking agent.

The total amount of the binder (including the cross-linking agent) in the magnetic layer of the present invention is 10 to 40% by weight, preferably 10 to 40% by weight, based on the ferromagnetic powder.
It is 15 to 30% by weight. If the compounding ratio of the binder is more than the above range, the degree of filling of the ferromagnetic powder is low and the electromagnetic conversion characteristics are reduced,
Conversely, when the amount is small, the running durability is reduced.

As the material of the nonmagnetic support, use is made of polyesters such as polyethylene terephthalate and polyethylene 2,6 naphthalate; polyolefins such as polyethylene and polypropylene; cellulose derivatives such as cellulose triacelate; and resins such as polycarbonate, polyimide and polyamideimide. It may be metallized with a metal such as aluminum as required, or may be a metal foil such as an aluminum foil or a stainless steel foil.

The form of the support may be any of tape, disk, film, sheet, card, drum, etc., and various materials are selected according to the form.

The thickness of the support is 3 to 100 μm, preferably 3 to 20 μm for a magnetic tape, and 20 to 100 μm for a magnetic disk, in the ranges usually used.

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 the Mohs hardness is 5 or more. Examples of inorganic particles having a Mohs hardness of 5 or more include Al ₂ O ₃ (Mohs hardness of 9), TiO (6), TiO ₂
(6.5), SiO ₂ (7), SnO ₂ (6.5), Cr ₂ O ₃ (9), and α-Fe ₂ O ₃ (5.5).
These can be used alone or in combination.

Particularly preferred are inorganic particles having a Mohs hardness of 8 or more. When inorganic particles having a Moh's hardness lower than 5 are used, the inorganic particles are easily dropped from the magnetic layer, and since there is almost no polishing effect of the head, head clogging is likely to occur, and running durability is poor. Become.

The content of the inorganic particles is usually in the range of 0.1 to 20 parts by weight, preferably 1 to 1 part by weight per 100 parts by weight of the ferromagnetic powder.
The range is 0 parts by weight.

It is desirable that the magnetic layer contains carbon black (particularly, nanometers having an average particle diameter of 10 to 300 nm; ^10-9 m) in addition to the above inorganic particles.

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

First, a ferromagnetic powder, a binder, and if necessary, other fillers, additives, and the like are kneaded and dispersed in a solvent to prepare a magnetic paint. As a solvent used in kneading, a solvent generally used for preparing a magnetic paint can be used.

The method of kneading is not particularly limited, and the order of addition of each component can be appropriately set.

For example, a lubricant, an additive or a cross-linking agent dissolved in an organic solvent may be prepared and added to a magnetic substance dispersion prepared with a solvent, a binder, a magnetic powder, etc. immediately before coating.

When preparing the magnetic paint, known additives such as a dispersant, an antistatic agent, and a lubricant can be used together.

Examples of the dispersant include fatty acids having 12 to 22 carbon atoms, salts or esterified compounds thereof and compounds in which some or all of the hydrogen atoms of the compounds are substituted with fluorine atoms, amides of the above fatty acids, aliphatic amines, higher alcohols , Polyalkylene oxide alkyl phosphate, alkyl phosphate, alkyl borate, sarcosinates,
Known dispersants such as alkyl ether esters, trialkyl polyolefins, oxyquaternary ammonium salts and lecithin, and low molecular weight epoxy compounds can be mentioned.

When a dispersant is used, it is usually used in an amount of 0.1 to 10 parts by weight based on 100 parts by weight of the ferromagnetic powder used.

Examples of the antistatic agent include conductive fine powders such as carbon black and carbon black graft polymer; natural surfactants such as saponin; alkylene oxides;
Nonionic surfactants such as glycerin and glycidol; higher alkylamines, quaternary ammonium salts, salts of pyridine and other heterocyclic compounds, cationic surfactants such as phosphonium or sulfonium; carboxylic acid, phosphoric acid, Anionic surfactants containing acidic groups such as sulfate groups and phosphate groups; amphoteric surfactants such as amino acids, aminosulfonic acids, and sulfuric acid or phosphate esters of amino alcohols; When using the above conductive fine powder as an antistatic agent, for example, 0.1 to 10 parts by weight per 100 parts by weight of ferromagnetic powder
It is used in the range of 0.1 to 10 parts by weight when the surfactant is used.

Note that the above-mentioned additives such as dispersants, antistatic agents, and lubricants are not strictly described under the limitation that they have only the above-described functions and effects. Alternatively, it may act as an antistatic agent. Therefore, the effects of the compounds and the like exemplified by the above classification are, of course, not limited to the items described in the above classification, and when a substance having a plurality of effects is used, the amount of addition is It is preferable to determine in consideration of the effect.

The magnetic paint thus prepared is applied on the above-mentioned non-magnetic support. At this time, a plurality of magnetic paints may be sequentially or simultaneously layer-applied.

The coating can be performed directly on the non-magnetic support, but can also be performed on the non-magnetic support via an intermediate layer such as an adhesive layer. The term "intermediate layer" as used herein refers to a layer of an adhesive alone or a composite film layer in which non-magnetic fine particles such as carbon are dispersed in a binder.

The intermediate layer containing carbon black can be arbitrarily selected from various binders used in the magnetic layer as the binder. The carbon preferably has a particle size of 10 to 50 nm (nanometer; 10 to 9 m), and the binder: carbon black preferably has a weight ratio of 100: 10 to 100: 150. The thickness of the intermediate layer is preferably 0.1 to 2 μm for a simple adhesive layer, and 0.5 to 4 μm for a composite layer containing a nonmagnetic powder.

In addition to the intermediate layer, a lubricant same as or different from the lubricant used for the magnetic layer may be added.

Details of the method for dispersing the ferromagnetic powder and the binder and the method for coating the support are described in JP-A-54-46011 and JP-A-54-46011.
-21805 and other publications.

The thickness of the magnetic layer applied in this manner is generally 0.5 to 10 μm in thickness after drying, usually 0.7 to 6.0 μm.
It is applied to be in the range of μm.

When the magnetic recording medium is used in the form of a tape, the magnetic layer coated on the non-magnetic support is usually dried after subjecting the ferromagnetic powder in the magnetic layer to orientation treatment, that is, a magnetic field orientation treatment. On the other hand, in the case of a disk-shaped medium, a non-orientation treatment by a magnetic field is performed to remove the anisotropy of the magnetic characteristics. Then, after a surface smoothing treatment is performed as necessary, a heat treatment and / or a curing treatment by irradiation with radiation are performed, if necessary, to cut into a desired shape.

On the surface of the non-magnetic support on which the magnetic layer is not provided,
A known back layer may be provided.

(Effects of the Invention) In the present invention, the magnetic layer contains an iron salt of a hydroxamic acid derivative, whereby the reproduction output is high, the friction coefficient under low temperature and low humidity of 10 ° C and 10% is improved, and the high temperature of 40 ° C and 90% is high. The coefficient of friction under wet conditions is also improved. In other words, the affinity between the iron salt of hydroxamic acid and the ferromagnetic powder is good, and the reproduction output is increased because the dispersibility is improved, and the hydrophobic portion of the hydroxamic acid derivative is preferably oriented outward on the surface of the magnetic layer. Lubrication performance is obtained.

〔Example〕

Next, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto.

In the examples, “parts” indicates “parts by weight”.

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

Magnetic paint composition Ferromagnetic alloy powder (composition: Fe94%, Zn4%, Ni2%; coercive force:
1500 Oe; specific surface area 54 m ² / g) 100 parts Vinyl chloride / vinyl acetate / maleic anhydride copolymer (Nippon Zeon Co., Ltd. 400X110A, degree of polymerization 400) (A) or vinyl chloride / vinyl acetate copolymer (polymerization) Degree 400)
(B) 12 parts polyester-based polyurethane (weight average molecular weight 40,000, number average molecular weight 25,000)
(Described in table) (C) 5 parts Coronate L 4 parts Abrasive (α-alumina, average particle diameter 0.3 μm) 5 parts Lubricant ・ ・ ・ ・ ・ (Table 1) Oleic acid 1 part Butyl stearate 1 part Carbon black (average particle size: 40 nm) 2 parts Methyl ethyl ketone 300 parts A magnetic coating is applied to a non-magnetic support, and the magnetic coating is undried, and the magnetic field is aligned with a 3000 gauss magnet. 8mm after performing
An 8 mm video tape was manufactured by slitting to width.

A 7 MHz signal was recorded on the video tape obtained as described above using a VTR (Fuji Photo Film Co., Ltd .: FUJIX-8) and reproduced. The relative playback output of the video tape when the playback output at 7 MHz recorded on the reference tape (sample No. 16) was set to 0 dB was measured.

The obtained video tape and the stainless steel pole were brought into contact with each other with a tension (T ₁ ) of 50 g (winding angle 180 °), and under this condition, the video tape was required to run at a speed of 3.3 cm / s. The tension (T ₂ ) was measured. Based on this measurement,
The friction coefficient μ of the video tape was determined by the following formula.

(Listed in Table 1) μ = 1 / π · 1n (T ₂ / T ₁ ) The friction coefficient test was performed at a.10 ° C., 10% RH, b, 40 ° C., 9
The test was performed under two conditions of 0% RH.

As is evident from the results in Table 1, all of the examples using the iron salt of the hydroxamic acid derivative of the present invention have a high regeneration output and a low friction coefficient under both ab conditions.

On the other hand, when only the fatty acid or ester is used without using the compound of the present invention, the reproduction output is low, and the friction coefficient is particularly large under high temperature and high humidity (condition b). Further, it can be seen that there are many problems such as the effect decreasing with time.

Further, it can be seen that the combination with the polar group-containing resin is preferable because the μ value at low temperature and low humidity and at high temperature and high humidity are further reduced.

Claims (2)

(57) [Claims] 1. A magnetic recording medium comprising a non-magnetic support and a magnetic layer provided on the support, wherein the magnetic layer holds an iron salt of a hydroxamic acid derivative represented by the following general formula: recoding media. Here, R represents a hydrocarbon group having 10 to 26 carbon atoms, and n represents an integer of 1 to 3. 2. A magnetic recording medium in which a magnetic layer comprising a ferromagnetic fine powder and a binder is provided on a non-magnetic support, wherein at least one kind of resin occupying 5 wt% or more of all resins of the binder. Is an epoxy group, at least one polar group of COOM, SO ₃ M, OSO ₃ M, PO ₃ M ₂ , and OPO ₃ M ₂ (where M is a hydrogen alkali metal or a substituted or unsubstituted ammonium, When there are a plurality of M in one group, they may be different from each other), and the magnetic layer is represented by the above general formula, wherein 10 ^-6 to 10 ^-4 equivalents are introduced per gram of the resin. A magnetic recording medium containing or retaining an iron salt of a hydroxamic acid derivative.