JP2601370B2 - Magnetic recording media - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a magnetic recording medium having a magnetic layer provided on a non-magnetic support, and particularly to a running property, durability and storage stability under a wide range of temperature and humidity conditions. It relates to an excellent magnetic recording medium.

(Prior art)

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 are required to have high video output and excellent electromagnetic conversion characteristics such as excellent original image reproduction capability. Have been.

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 fat, and shark oils and vegetable oils have been used as lubricants.

When the amount of the conventional lubricants described above is small, the lubricating effect is low, and when the amount of the lubricant is increased to enhance the effect, the mechanical strength of the magnetic coating film is weakened, the magnetic layer is shaved, and the shaving powder contaminates the traveling path. In addition, sufficient durability for 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 increase lubricity, they must be used in large amounts, in which case the magnetic layer becomes softer due to the plasticity effect, and the mechanical strength increases. And the durability of the still reproduction deteriorates.

JP-A-1-248315 discloses an N, N dialkylamidated higher fatty acid for improving running durability. It has been proposed to use for a magnetic layer. However, there were the following problems. That is, the reproduction output is good, but low temperature and low humidity (5 ° C, 10% RH) and high temperature hard (45 ° C, 90%
RH), the coefficient of friction tended to increase, and head clogging often occurred at low temperature and low humidity (10 ° C, 10% RH) and low temperature hard (10 ° C, 70% RH).

Japanese Patent Publication No. 55-22851 discloses a methylene bisamide of a higher fatty acid having no plasticizer effect as a lubricant. Has been proposed for use in magnetic layers.

However, it was impossible to improve the friction coefficient increase at low temperature and low humidity and high temperature and high humidity, and the clogging of the head at low temperature and low humidity and low temperature and high humidity.

With the recent popularization and generalization of flexible disk drive units for consumer use such as those for VTRs, personal computers, and word processors, the use conditions of magnetic recording media are expected to be widespread, such as use at 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, but such a conventionally known lubricant is sufficient. However, there is a problem that the performance is deteriorated.

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.

Therefore, the present inventors have conducted intensive studies on a lubricant that solves the problems of the magnetic powder coating type and the metal thin film type, and as a result, the conventional lubricant can be achieved at all by including or holding a urea derivative in the magnetic layer. It has been found that excellent durability and environmental adaptability can be obtained, and the present invention has been accomplished.

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

(Constitution of the Invention) An object of the present invention is to provide a magnetic recording medium having a nonmagnetic support and a magnetic layer provided on the support, wherein the magnetic layer contains or holds a urea derivative represented by the following general formula. This can be achieved by a characteristic magnetic recording medium.

(Where R is a hydrocarbon group having 10 to 26 carbon atoms) R 'is hydrogen or a hydrocarbon group having 1 to 26 carbon atoms) More preferably, the magnetic layer contains a ferromagnetic powder and a binder, and the binder At least one of the resins occupying 5 wt% or more of the total resin is an epoxy group, -COOM, SO
_At least one polar group of ₃ M, -OSO ₃ M, -PO ₃ M ₂ , and -OPO ₃ M ₂ (where M is hydrogen, an alkali metal, or a substituted or unsubstituted ammonium, and Wherein a plurality of M may be different from each other), the resin being introduced in an amount of 10 ^-7 to 10 ^-3 equivalent per gram of the resin.

Also, the present invention can be achieved by a magnetic recording medium, wherein the binder in the magnetic layer contains a hardener in an amount of 2 to 10% by weight based on the ferromagnetic powder.

The magnetic recording medium is characterized in that the magnetic layer is a ferromagnetic metal thin film formed by oblique evaporation.

In other words, the urea group, which is a polar group of the urea derivative of the present invention, is weaker in acidity than carboxylic acid, sulfonic acid, phosphoric acid, and the like, but has high affinity with inorganic materials and corrodes metal materials because it is polarized in the molecule. It adheres to the surface without any problem and the hydrocarbon group of the hydrophobic chain is oriented on the surface.

In addition, the urea derivative of the present invention hardly adsorbs to a ferromagnetic substance due to weak acidity of a coating type magnetic recording medium, and has an affinity for a binder, so that it is easily oriented on the surface. In particular, when a binder (binder) containing a polar group is used, the effect is remarkably exhibited.

This is because the lubricating performance can be maintained by the anchor effect of having very strong interaction with the polar group of the compound of the present invention. On the other hand, carboxylic acid, phosphoric acid, sulfonic acid and the like do not appear on the surface because they are strongly adsorbed on the ferromagnetic powder.

Further, as described above, the urea derivative of the present invention has a strong interaction with a binder, has an anchor effect, and has a structure as described above. And the presence of free amino groups, it is easy to react with polyisocyanate as a curing agent, or the durability of the magnetic layer is remarkably improved. This is because the urea derivative of the present invention does not simply adsorb but chemically reacts, so that an extremely strong anchor effect is obtained, and a good lubricating effect is exhibited because the hydrophobic chains are aligned outward. . Also, in the metal thin film medium, the urea derivative of the present invention has a high affinity for inorganic materials due to intramolecular polarization, while it is not acidic, so that it does not corrode metals and is oriented on the surface, which is favorable. It has lubricating properties, and its effect lasts.

As the urea derivative of the present invention, R can be selected irrespective of the molecular weight, branched structure, unsaturated bond, and isomer structure as long as it is a urea derivative having a hydrocarbon group of 10 or more and 26 or less.
Preferably, it is a non-aromatic hydrocarbon group (however, an aralkyl group and the like are included), and a linear alkyl group is particularly preferable.

In this case, if the number of carbon atoms is 9 or less or 27 or more, the hydrophobic chain is too short or too long, so that the orientation becomes difficult and the lubricity is not exhibited.

R can be selected from hydrogen or a urea derivative of a hydrocarbon group of 1 or more and 26 or less irrespective of the molecular weight, branched structure, unsaturated bond, and isomer structure. It is a hydrocarbon group (however, an aralkyl group and the like are included), and a linear alkyl group is particularly preferable. Among them, more preferably, hydrogen or an alkyl group having 1 to 4 or 10 to 26 carbon atoms is preferable from the viewpoint of orienting the hydrophobic chain at a high density. The total number of carbon atoms is preferably 44 or less. If it is more than 44, the solubility in the solvent and the binder is deteriorated, so that it is deposited on the surface, and the orientation becomes difficult, and it becomes difficult to exhibit the lubricity.

In particular These compounds can be obtained, for example, by dissolving in a monoalkylamine solvent (alcohol, acetone, MEK, etc.), adding glacial acetic acid or hydrochloric acid, then adding an aqueous solution of sodium cyanate dropwise, followed by filtration and recrystallization. .

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 top-coating the surface of the magnetic layer of the coating type magnetic recording medium, ² to 50 mg / m ² is appropriate.

If the amount used exceeds this range, the surface of the sulfoxide derivative will be excessive, and not only may cause sticking and failure such as moisture absorption, but also in the case of the internal addition type, due to the action of plasticizing the magnetic layer binder. On the contrary, there is a problem that the durability is lowered.

If the amount used falls below this range, the surface amount is naturally insufficient and the effect cannot be obtained.

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 (including various monoesters, sorbitan, glycerin,
Fatty acid esters of isopolyesters, 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 oils, higher aliphatic amines; inorganic fine powders such as graphite, silica, molybdenum disulfide, tungsten disulfide; polyethylene, polypropylene, polyvinyl chloride, ethylene-vinyl chloride copolymer, poly Resin fine powder such as tetrafluoroethylene; α-olefin polymer; unsaturated aliphatic hydrocarbon which is liquid at normal temperature, terminal-modified or unmodified perfluoroalkyl polyether, 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 1/10 of the urea derivative of the present invention.
Double the amount used.

In the present invention, as a method of retaining the urea derivative in the magnetic layer, there are a method of containing the urea derivative in the magnetic layer, a method of applying a top coat on the surface (a method of dissolving the material in an organic solvent, applying or spraying the solution on a substrate, and then drying the material, (A method in which a substrate is immersed in a solution of a material dissolved in an organic solvent to adsorb the material on the substrate surface, a Langmuir-Blodget method, etc.).

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.

As an example of the ferromagnetic alloy powder, a metal content is 75 wt% or more, and a metal content of 80 wt% or more is 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, S
b, B, Ba, Ta, W, Re, Au, Hg, Pb, P, La, ce, Pr, Nd, Te, Bi etc.)
And the like. 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 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, but a needle shape and a plate shape are preferable in terms of electromagnetic conversion characteristics. The crystallite size and specific surface area are not particularly limited, but the crystallite size is preferably 400 mm or less, and SBET is preferably 30 m ² / g or more. The pH and surface treatment of the ferromagnetic powder can be used without any particular limitation (the surface treatment may be performed with a substance containing an element such as titanium, silicon, or aluminum, or carboxylic acid, sulfonic acid, sulfate ester, phosphonic acid, It may be treated with an organic compound such as an adsorptive compound having a nitrogen-containing heterocycle such as a phosphoric acid ester or benzotriazole.
The preferred pH range is 5-10. In the case of ferromagnetic iron oxide fine 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 1
It is 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 copolymer of vinyl chloride and vinylidene chloride, and a mixture of vinyl chloride and vinyl chloride. Acrylonitrile copolymer, vinyl copolymer such as ethylene-vinyl acetate copolymer, nitrocellulose, cellulose acetate propionate, cellulose derivative such as cellulose acetate butyrate resin, acrylic resin, 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, rubber resin such as butadiene acrylonitrile resin, silicone resin,
Fluorinated resins can be mentioned.

Among these, a vinyl chloride resin is preferable because of high dispersibility of the ferromagnetic 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 System reaction resin, epoxy-polyamide resin, nitrocellulose melamine resin, mixture of high molecular weight polyester resin and isocyanate prepolymer, urea formaldehyde resin, mixture of low molecular weight glycol / high molecular weight diol / polyisocyanate, polyamine resin, and mixtures thereof can give.

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
OM, OH, NR ₂ , NR ₃ X, SO ₃ M, OSO ₃ M, PO ₃ M ₂ , OPO ₃ M ₂ , where M is hydrogen, alkali metal or substituted or unsubstituted ammonium, and When a plurality of Ms are present, they may be different from each other. X represents a halogen ion.
(R is hydrogen or an alkyl group). The effect of adding the urea derivative of the present invention, which is preferable in terms of dispersibility and durability of the ferromagnetic powder, is remarkably exhibited. The content of the polar group is preferably from 10 ^-7 to 10 ^-3 equivalents, more preferably from 10 ^-6 to 10 ^-4 equivalents, per gram of the polymer.

When the content of the polar group is less than 10 ^-7 equivalent, the amount of the interacting lubricant becomes small, so that it is difficult to form a uniform alignment film and the slipperiness is reduced. On the other hand, if the amount is more than 10 ^-3 equivalent, the viscosity of the binder increases and the dispersibility decreases, which is not preferable.

The above-listed polymer binders 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 monomer.

As the isocyanate-based crosslinking agent, a polyisocyanate compound having two or more isocyanate groups, for example, tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, hexamethylene diisocyanate,
Xylene diisocyanate, naphthylene-1,5-diisocyanate, o-triidine diisocyanate, isophorone diisocyanate, isocyanates such as triphenylmethane diisocyanate, the reaction product of these isocyanates with polyalcohol, and the condensation of these isocyanates Generated polyisocyanate. 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, Millionate MR, Millionate MTL, Daltsec 1350, Daltsec 2170, Daltsec 2280, Takeda Pharmaceutical Co., Ltd. Takenate D102, Takenate D110N, Takenate D200,
Takenate D202, Sumitomo Bayer Co., Ltd., Sumidur N75, West German Bayer Co., Ltd., DeathModule L, DeathModule IL, DeathModule N, DeathModule HL, Dainippon Ink and Chemicals, Inc., Burnock D850, Burnock D802, etc. It is marketed under the trade name.

The amount of these crosslinking agents is preferably in the range of 2 to 10 parts by weight with respect to 100 parts by weight of the ferromagnetic powder, particularly from the viewpoint of bonding with the lubricant. If it is more than this, the self-condensation product of the cross-linking agent increases, the amount of the lubricant bonded thereto increases, the LuB surface amount decreases, and the durability decreases.

In addition, when the amount is less than this, the amount that bonds with the lubricant decreases, and the anchor effect cannot be expected, and the durability under severe conditions is reduced.

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, diethylene glycol di (meth) acrylate and triethylene glycol di (meth) having two or more (meth) acryloyl groups are preferable.
(Meth) acrylates of polyethylene glycol such as acrylate, trimethylolpropane tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaneerythritol penta (meth) acrylate, dipentaerythritol hexa (meth) acrylate, polyisocyanate And a reaction product of a compound with a hydroxy (meth) acrylate compound.

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 blending ratio of the binder is larger than the above range, the degree of filling of the ferromagnetic fine powder is low, and the electromagnetic conversion characteristics are deteriorated.

As the material of the non-magnetic support, it is possible to use polyesters such as polyethylene terephthalate and polyethylene 2,6 naphthalate; polyolefins such as polyethylene and polypropylene; cellulose derivatives such as cellulose triacetate; and resins such as polycarbonate, polyimide and polyamide imide. It can be metallized with a metal such as aluminum if necessary, or 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 nonmagnetic support is 3 to 100 μm, preferably 3 to 20 μm for a magnetic tape, and 20 to 100 μm for a magnetic disk.
μ is a normally 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 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), and 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 (especially one having an average particle diameter of 10 to 300 nm (nanometer; 10 ^-9 m)) and the like in addition to the 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 solution prepared by dissolving a lubricant, an additive, or a cross-linking agent in an organic solvent may be prepared and added to a ferromagnetic powder dispersion prepared with a solvent, a binder, a ferromagnetic powder, or the like, immediately before application.

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 compound are substituted with fluorine atoms, amides of the above aliphatic acids, aliphatic amines, Higher alcohol, 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 using a dispersant, use the ferromagnetic powder that is normally used.
It is used in the range of 0.1 to 10 parts by weight based on 100 parts by weight.

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 an acidic group such as a sulfate group or a phosphate group: Examples of the anionic surfactant include amino acids, aminosulfonic acids, and sulfuric acid or phosphate esters of amino alcohol. 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 particle size of the carbon black is preferably from 10 to 500 nm (nanometer; ^10-9 m), and the binder: carbon black is preferably from 100: 10 to 100: 150 by weight. The thickness of the intermediate layer is 0.1 to 2 μm for a simple adhesive layer.
m, in the case of a composite layer containing a nonmagnetic powder, the thickness is preferably 0.5 to 4 μm.

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 in the range of about 0.5 to 10 μm in terms of the 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. Conversely, in the case of a disk-shaped medium, a non-orientation treatment by a magnetic field is performed in order to remove magnetic properties.
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.

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

In the present invention, the incident angle is generally preferably 45 ° to 90 °, and particularly the incident angle θmax is 60 ° to 90 °, the incident angle θmin
Is preferably 45 ° to 75 °.

As the ferromagnetic metal thin film material used in the present invention, F
Metals such as e, Co, Ni, or Fe-Co, Fe-Ni, Co-N
i, Fe-Co-Ni, Fe-Rh, Fe-Cu, Co-Cu, Co-Au, Co
-Y, Co-La, Co-Pr, Co-Gd, Co-Sm, Co-Pt, Ni-
Cu, Mn-Bi, Mn-Sb, Mn-Al, Fe-Cr, Co-Cr, Ni-C
r, ferromagnetic alloys such as Fe-Co-Cr, Ni-Co-Cr, and Fe-Co-Ni-Cr. Particularly preferred is Co or an alloy containing 75% by weight of Co. The total thickness of the laminated ferromagnetic metal thin film is generally from about 0.02 μm to 5.0 μm, preferably from about 0.02 μm to 5.0 μm, since it is necessary to have a thickness capable of providing a sufficient output as a magnetic recording medium and a sufficient thickness for high-density recording. Is
It is from 0.05 μm to 2.0 μm. The thickness of each magnetic thin film may be designed to be equal, or may be provided with a thickness of ± 50% of the ferromagnetic metal thin film closest to the base.

The vapor deposition in the present invention means, in addition to the ordinary vacuum vapor deposition described in the specification of the above-mentioned U.S. Pat.No. 3,334,32, the vaporization is performed by ionizing or accelerating the vapor flow by electric field, magnetic field or electron beam irradiation or the like. The method also includes a method of forming a ferromagnetic metal thin film on a supporting substrate in an atmosphere having a large mean free path of molecules, for example, an electric field vapor deposition method as disclosed in Japanese Patent Application Laid-Open No. 51-149008. JP-A-43-11
No. 525, JP-B-46-29484, JP-B-47-26579, JP-B-49-45439, JP-A-49-33890, JP-A-49-34483
And the ionized vapor deposition method disclosed in JP-A-49-54235 can also be used in the present invention.

As the substrate used for the ferromagnetic metal thin film of the present invention, polyethylene terephthalate, polyimide, polyamide,
Plastic bases such as polyvinyl chloride, cellulose triacetate, polycarbonate, polyethylene naphthalate are preferred. Particularly in the present invention, the surface roughness (Ra)
The above-mentioned flexible plastic base having a particle size of 0.012 μm or less is preferable. Here, the surface roughness (Ra) is JIS-BO6
The center line average roughness shown in item 5 of 01, and the cutoff is 0.25 mm. Further, an undercoat layer provided on the plastic base and having a surface roughness (Ra) of 0.012 μm or less may be used as the base.

Further, in the present invention, a nonmagnetic layer may be interposed between the laminated ferromagnetic metal thin films. Preferred as the nonmagnetic intermediate layer are Cr, Si, Al, Mn, Bi, Ti, Sn, Pb, and I.
It is composed of n, Zn, Cu or their oxides and ceramics.

(Effect of the Invention) The urea derivative of the present invention has a strong interaction with a binder due to intramolecular polarization in a coating type medium, has an anchor effect, and has a structure. The durability of the magnetic layer is remarkably improved because it has a free amino group and easily reacts with the polyisocyanate as a curing agent, and it has low temperature and low humidity (10 ° C, 10% RH) and low temperature and high humidity (10
°, 70% RH). Good lubrication properties are exhibited because the hydrophobic chains of the urea derivative are aligned outward, and low temperature and low humidity (5 ° C 10RH) and high temperature and high humidity (45 ° C) , 90% RH). Also, the urea derivative of the present invention has a high affinity for inorganic materials and does not show acidity in a metal thin-film type medium due to intramolecular polarization, and therefore does not cause metal corrosion, and therefore does not rust. In addition to this, the μ value at low temperature and low humidity and at high temperature and high humidity are improved.

〔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 mg / m ² ) 100 parts vinyl chloride / vinyl acetate / maleic anhydride copolymer (Nippon Zeon Co., Ltd. 400 × 110A, 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 Lubricants ... (listed in 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 paint is applied to a non-magnetic support, and the magnetic paint is undried, and the magnetic field is aligned with a 3000 gauss magnet. 8mm after performing
8mm video tape was manufactured by slitting to width.

Example 2 A cobalt-nickel magnetic film (150 nm thick) was obliquely deposited on a 13 μm-thick polyethylene terephthalate film to prepare a raw material of a magnetic recording medium. An electron beam evaporation source is used as a deposition source, and a cobalt-nickel alloy (Co: 80 wt%, Ni: 20%) is charged into the evaporation source and the degree of vacuum is 5 × 10 ⁻⁵ T.
Oblique deposition was performed in an oxygen stream in an orr so that the incident angle was 50 degrees. Various materials are dissolved in methyl ethyl ketone and applied on the magnetic metal thin film of the raw material of the obtained magnetic recording medium,
Samples prepared by drying were prepared and designated as Sample Nos. 32 to 47 (Table 2).

The video tape obtained as described above and the stainless steel pole are contacted with a tension (T ₁ ) of 50 g (winding angle 180 °)
Then, under these conditions, the tension (T ₂ ) required for running the video tape at a speed of 3.3 cm / s was measured. Based on the measured values, the friction coefficient μ of the video tape was determined by the following formula. (Described in Tables 1 and 2) μ = 1 / π · 1n (T ₂ / T ₁ ) The friction coefficient was tested at a.5 ° C., 10% RH, b.45 ° C., 90
% RH was performed under two conditions.

Also, set the temperature to 20 to check the corrosion of the tape to the magnetic material.
The tape left for one week in a thermostat whose humidity changes from 10% to 100% from ° C to 40 was observed under a microscope, and the rust condition was compared with the reference tape (41) as 100, and the amount of rust was relatively compared.

Evaluation of head clogging is 10 ℃, 10% environment and 10 ℃,
Recording (rewind after recording) for 10 minutes in a 70% environment, and playback for 10 minutes. During reproduction, the number of seconds in which the output was lost due to head clogging was measured in total, and this was evaluated as head clogging.

As is clear from the results in Tables 1 and 2, it can be seen that the examples using the urea derivative of the present invention have a low coefficient of friction under both a and b conditions and do not corrode the tape.

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). It can be seen that sulfonic acid and phosphonic acid corrode the tape.

Claims (4)

(57) [Claims] 1. A magnetic recording medium comprising a nonmagnetic support and a magnetic layer provided on the support, wherein the magnetic layer contains or holds a urea derivative represented by the following general formula: . (Where R is a hydrocarbon group having 10 to 26 carbon atoms) R 'is hydrogen or a hydrocarbon group having 1 to 26 carbon atoms) 2. The magnetic layer comprises a ferromagnetic powder and a binder,
And at least one of the resins occupying 5 wt% or more of the total resin of the binder is an epoxy group, -COOM, SO ₃ M,-
At least one polar group of OSO ₃ M, —PO ₃ M ₂ , and —OPO ₃ M ₂ (where M is hydrogen, an alkali metal, or a substituted or unsubstituted ammonium; May be different from each other when M is present) per gram of resin
The magnetic recording medium according to claim 1, wherein the resin is a resin introduced in an amount of 10 ^-6 to 10 ^-4 equivalent. 3. The magnetic recording medium according to claim 2, wherein the binder in the magnetic layer contains a hardener in an amount of 2 to 10% by weight based on the ferromagnetic powder. 4. The magnetic recording medium according to claim 1, wherein said magnetic layer is a ferromagnetic metal thin film formed by oblique vapor deposition.