JPH0640377B2 - Magnetic recording medium - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a tape, sheet, card, drum or disk-shaped magnetic recording medium in which a magnetizable layer in which fine powdery magnetic particles are dispersed is laminated in a binder. It is a thing.
More specifically, the present invention relates to a magnetic recording medium obtained by curing the magnetizable layer with an actinic ray such as ultraviolet ray and then completely curing it by heat treatment.

(Prior Art) Conventionally, as binders for magnetic recording media, ethyl cellulose, nitro cellulose, polyvinylidene chloride resin, vinyl chloride-vinyl acetate copolymer, styrene-butadiene copolymer, polymethacrylic acid methyl resin, chloride Vinylidene-methyl methacrylate copolymers, polyurethane resins, epoxy resins, polyester resins, butadiene-acrylonitrile copolymers, etc. have been used, but these binders only solidify the resin component by evaporation of the solvent. Therefore, there is a drawback that the adhesion of the magnetic recording layer is insufficient.

On the other hand, a method has been proposed in which an isocyanate compound is added as a crosslinking reaction agent to the binder to improve the adhesion and physical properties with the support (Japanese Patent Publication No. 47-28048, etc.), but these methods add the reaction compound. Therefore, another drawback is that the pot life of the magnetic paint becomes short.

Further, there is a method of using an ultraviolet curable resin as a binder as described in JP-A-56-8466, but in this method, in a magnetic coating material containing a large amount of fine powder magnetic particles, an ultraviolet ray There is a fatal defect that penetration is insufficient and it cannot be completely cured.

Separately, Japanese Examined Patent Publication No. 57-50801 discloses a method of curing with an electron beam using a radiation-polymerizable resin as a binder. However, this method not only requires enormous equipment but is difficult to control the curing. However, there is a defect that the binder and the support are deteriorated at the same time as the curing.

On the other hand, the present inventors have already prepared an epoxy compound (A) having at least two epoxy groups in the molecule and a photopolymerizable compound (B) having a carboxyl group in the molecule or the compound.
It has been proposed to use a curable resin composition comprising a mixture of (B) and another photopolymerizable compound (C) and a photoinitiator as a binder for a magnetic recording medium.

(Problems to be Solved by the Invention) The curing of the binder is carried out by first activating the photopolymerizable compound (B) having a carboxyl group in the molecule or the compound (B) and another photopolymerizable compound (C) with an actinic ray. It is a two-step process including a reaction to polymerize by irradiation to form a carboxyl group-containing polymer, and then a reaction in which the epoxy compound (A) reacts with the carboxyl group-containing polymer to completely cure by heating. However, the first step reaction, that is, the photopolymerizable compound (B) having a carboxyl group in the molecule or the compound
(B) and the other photopolymerizable compound (C) is cured by irradiation with actinic rays to form a carboxyl group-containing polymer, the actinic rays are shielded by the fine powder magnetic particles contained in a large amount, the coating film It has been found that there is a drawback in that the polymerization does not always proceed sufficiently to the lower layer portion of the above, and therefore the hardness is not sufficient even when the coating film is cured by the second heating.

(Means for Solving the Problems) In view of such a situation, the present inventors have a long pot life, can easily control the curing reaction without problems in equipment, and are different from conventional UV curable binders. Fully cured despite containing a large amount of fine powder magnetic particles,
Moreover, as a result of intensive studies to find a new binder that obtains sufficient coating hardness, by adding a compound having the structural formula (I) to the curable resin composition, it is possible to solve the above defects. Found and arrived at the present invention.

That is, according to the present invention, in a magnetic recording medium obtained by coating a magnetic coating material on a non-magnetic support and curing the magnetic coating material, the magnetic coating material has 2
Epoxy compound having one or more epoxy groups (A) and a photopolymerizable compound having a carboxyl group in the molecule (B) or a mixture of the compound (B) and another photopolymerizable compound (C) and a structural formula ( A magnetic recording medium comprising a curable resin composition containing a compound (D) represented by I) and a fine powder magnetic powder particles (E) uniformly dispersed and contained therein.

(However, R ₁ , R ₂ , R ₃ or R ₄ represents an alkyl group having 1 to 12 carbon atoms.) An epoxy compound (A) having two or more epoxy groups in the molecule used in the present invention Has two epoxy groups in one molecule
It is an epoxy compound having one or more, and the epoxy equivalent thereof is 100 to 4,000, preferably 100 to 1,000.

Typical compounds include bisphenol A, bisphenol F, halogenated bisphenol A, phenol novolac, cresol novolac, polyepoxy compounds of polyhydric alcohol, N, N, N ', N'-tetraglycidyl. Examples include aminopolyepoxy compounds such as meta-xylene diamine, N, N, N ', N'-tetraglycidyl 1,3-bis (aminomethyl) cyclohexane and the like. These epoxy compounds can be used alone or in combination of two or more.

Further, an epoxy compound having one epoxy group in the molecule, such as allyl glycidyl ether and phenyl glycidyl ether, can be used in combination.

Among these epoxy compounds having two or more epoxy groups in the molecule, preferred epoxy compounds include diglycidyl ether of bisphenol A, phenol novolak type polyepoxy compound, cresol novolak type polyepoxy compound, and polyvalent polyepoxy compound. Examples include polyepoxy compounds of alcohol.

Examples of the photopolymerizable compound (B) having one or more carboxyl groups in the molecule used in the present invention include (i) unsaturated compounds such as acrylic acid, methacrylic acid, itaconic acid, crotonic acid and fumaric acid. There are carboxylic acid compounds and (ii) compounds represented by the following general formula (II).

(In the formula, R ₁ represents hydrogen or a methyl group, R ₂ and R ₃ each represent an aliphatic, aromatic, or alicyclic residue, A represents an ester bond, and m and n each represent 1 to 1). Represents a positive integer of 3.) In the general formula (II), R ₂ has 2 to 10 carbon atoms 2
To a tetravalent hydrocarbon group or a hydroxyl group-containing hydrocarbon group, R ₃ is a divalent to tetravalent aliphatic polybasic acid residue having 2 to 10 carbon atoms, and 6 to 15 carbon atoms.
Is preferably a divalent to tetravalent aromatic polybasic acid residue or a divalent to tetravalent alicyclic polybasic acid residue having 6 to 10 carbon atoms.

Examples of the compound represented by the general formula (II) include the following compounds.

Examples of the compound of m = 1 and n = 1 are abbreviated as succinic acid monoacryloyloxyethyl ester and succinic acid monomethacryloyloxyethyl ester [hereinafter referred to as succinic acid mono (meth) acryloyloxyethyl ester]. ], Phthalic acid mono (meth) acryloyloxyethyl ester, maleic acid mono (meth) acryloyloxyethyl ester, tetrahydrophthalic acid mono (meth) acryloyloxyethyl ester, hexahydrophthalic acid mono (meth) acryloyloxyethyl ester Endo-bicyclo [2,2,1] -5-heptene-2,3-dicarboxylic acid mono (meth) acryloyloxyethyl ester, tetrahydrophthalic acid mono-2-
(Meth) acryloyloxy-1- (phenoxymethyl) ethyl ester, phthalic acid mono-2-hydroxy-
3- (meth) -acryloyloxypropyl ester,
Examples include succinic acid mono-2-hydroxy-3- (meth) acryloyloxypropyl ester.

Examples of the compound having m = 1 and n = 2 include trimellitic acid mono-2- (meth) acryloyloxyethyl ester and propane-1,2,3-tricarboxylic acid mono-1- (meth) acryloyloxyethyl ester. .

Examples of the compound of m = 1 and n = 3 include pyromellitic acid mono-2- (meth) acryloyloxyethyl ester, pentane-1,2,3,5-tetracarboxylic acid mono-1-
(Meth) acryloyloxyethyl ester and the like.

Examples of the compound in which m = 2 and n = 1 include phthalic acid mono- [2,3-bis (meth) acryloyloxyisopropyl] ester and methyltetrahydrophthalic acid mono-
[2,3-Bis (meth) acryloyloxyisopropyl] ester, tetrahydrophthalic acid mono- [2,3-
Examples thereof include bis (meth) acryloyloxyisopropyl] ester and succinic acid mono [2,3-bis (meth) acryloyloxyisopropyl) ester.

Examples of the compound having m = 2 and n = 2 include trimellitic acid mono- [4,5-bis (meth) acryloyloxyneopentyl] ester and trimellitic acid mono- [3,4-
Bis (meth) acryloyloxyisobutyl] ester and the like.

Examples of compounds in which m = 3 and n = 2 include trimellitic acid mono- [3,4,5-tris (meth) acryloyloxyneopentyl] ester, propane-1,2,3-tricarboxylic acid di-1, 2- (meth) acryloyloxyethyl ester and the like.

Examples of the compound of m = 3 and n = 3 include pyromellitic acid mono- [3,4,5-tris (meth) acryloyloxyneopentyl] ester and pentane-1,2,3,5-tetracarboxylic acid tris. -1,2,5- (meth) acryloyloxyethyl ester and the like.

As the photopolymerizable compound (B) having one or more carboxyl groups in the molecule, the compound (ii) is particularly preferable among the above compounds. These photopolymerizable compounds (B) having a carboxyl group in the molecule may be used alone or in combination of two or more kinds, or in combination with one or more kinds of other photopolymerizable compounds (C) described later. You can

The amount of the photopolymerizable compound (B) having one or more carboxyl groups in the molecule in the photopolymerizable compound (B + C) used in the present invention is 10 to 100% by weight. If the blending amount is less than 10% by weight, the adhesion of the resulting cured coating film will be insufficient.

The photopolymerizable compound (C) used in the present invention is 1 in the molecule.
A photopolymerizable compound having one or more photopolymerizable double bonds.

Examples of the photopolymerizable compound having one photopolymerizable double bond in the molecule include (i) styrene compounds such as styrene, α-methylstyrene and chlorostyrene, and (ii) methyl (meth) acrylate. , Ethyl (meth) acrylate, n- and i-propyl (meth) acrylate, n
-, Sec- and t-butyl (meth) acrylate, 2
-Alkyl (meth) acrylates such as ethylhexyl (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, alkoxy such as methoxyethyl (meth) acrylate, ethoxyethyl (meth) acrylate, butoxyethyl (meth) acrylate Alkyl (meth) acrylates, allyloxyalkyl (meth) acrylates such as phenoxyethyl (meth) acrylate, hydroxyalkyl (meth) acrylates such as 2-hydroxyethyl (meth) acrylate, halogen-substituted alkyl (meth) acrylates, Or polyethylene glycol mono (meta)
Acrylate, polypropylene glycol mono (meth)
Polyoxyalkylene glycol mono (meth) acrylates such as acrylates, substituted alkyl mono (meth) acrylates such as alkoxypolyoxylalkylene mono (meth) acrylates, heterocycle-containing (meth) such as tetrahydrofurfuryl (meth) acrylate
Hydrogenation of acrylates, (iii) mono (meth) acrylates of alkylene oxide adducts of bisphenol A such as ethylene oxide and propylene oxide adducts of bisphenol A, ethylene oxide and propylene oxide adducts of hydrogenated bisphenol A Mono (meth) acrylates of alkylene oxide adducts of bisphenol A, (iv) diisocyanate compounds and 1
One (meth) acryloyloxy group in the molecule obtained by further reacting the terminal isocyanate group-containing compound obtained by previously reacting one or more alcoholic hydroxyl group-containing compounds with an alcoholic hydroxyl group-containing (meth) acrylate Urethane-modified mono (meth) acrylates having, (v) epoxy mono (meth) acrylates obtained by reacting a compound having one or more epoxy groups in the molecule with acrylic acid or methacrylic acid, and (vi) Examples include oligoester mono (meth) acrylates obtained by reacting acrylic acid or methacrylic acid and a polyvalent carboxylic acid as a carboxylic acid component with a divalent or higher polyvalent alcohol as an alcohol component.

Examples of the photopolymerizable compound having two photopolymerizable double bonds in the molecule include (i) ethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, and 1,4-butanediol di ( Alkylene glycol di (meth) acrylates such as (meth) acrylate, neopentyl glycol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate,
Polyoxyalkylene glycol di (meth), such as diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, dipropylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate Substituted alkylene glycol di (meth) acrylates such as acrylates and halogen-substituted alkylene glycol di (meth) acrylates, and (ii) ethylene oxide and propylene oxide adducts of bisphenol A, etc. Bisphenol A alkylene oxide adduct di (meth) acrylates,
Di (meth) acrylates of hydrogenated bisphenol A alkylene oxide adducts such as ethylene oxide and propylene oxide adducts of bisphenol A,
(iii) Two in the molecule obtained by further reacting a terminal isocyanate group-containing compound obtained by previously reacting a diisocyanate compound with two or more alcoholic hydroxyl group-containing compounds with an alcoholic hydroxyl group-containing (meth) acrylate Urethane-modified di (meth) acrylates having a (meth) acryloyloxy group, (iv) a compound having two or more epoxy groups in the molecule, acrylic acid or /
And epoxy di (meth) acrylates obtained by reacting methacrylic acid, (v) acrylic acid or methacrylic acid as a carboxylic acid component and a polyvalent carboxylic acid, and a divalent or higher polyhydric alcohol as an alcohol component There are oligoester di (meth) acrylates and the like.

Examples of the photopolymerizable compound having three or more photopolymerizable double bonds in the molecule include (i) trimethylolpropane tri (meth) acrylate, trimethylolethanetri (meth) acrylate, pentaerythritol tetra (meta). ) Poly (meth) acrylates of trivalent or more aliphatic polyhydric alcohols such as acrylates, poly (meth) acrylates of trivalent or more halogen-substituted aliphatic polyhydric alcohols, (ii) diisocyanate compound and three or more Urethane having 3 or more (meth) acryloyloxy groups in the molecule obtained by further reacting a terminal isocyanate group-containing compound obtained by previously reacting an alcoholic hydroxyl group-containing compound with an alcoholic hydroxyl group-containing (meth) acrylate Modified poly (meth) acrylates, (iii)
There are epoxy poly (meth) acrylates obtained by reacting a compound having three or more epoxy groups in the molecule with acrylic acid or / and methacrylic acid.

The compounding ratio of the epoxy compound (A) used in the present invention and the photopolymerizable compound having a carboxyl group in the molecule (B) or a mixture of (B) and another photopolymerizable compound (C) is an epoxy compound. (A): Photopolymerizable compound [(B) or (B) + (C)] = 1
It is in the range of 0:90 to 90:10 (weight ratio), preferably epoxy compound (A): photopolymerizable compound [(B) or
(B) + (C)] = 20:80 to 80:20 (weight ratio). When the compounding amount of the epoxy compound (A) is less than 10% by weight, the reaction between the photopolymerizable compound (B) having a carboxyl group in the molecule and the epoxy compound (A) is substantially too small, the adhesiveness, etc. It is difficult to obtain an excellent cured coating film.

The compound (D) represented by the structural formula (I) used in the present invention includes 3,3 ′, 4,4′-tetra (methylperoxycarbonyl) benzophenone, 3,3 ′, 4,4′- Tetra (ethylperoxycarbonyl) benzophenone, 3,3 ', 4,4'
-Tetra (n-propylperoxycarbonyl) benzophenone, 3,3 ', 4,4'-tetra (i-propylperoxycarbonyl) benzophenone, 3,3', 4,4'-tetra (n-butylperoxy) Carbonyl) benzophenone, 3,3 ', 4,4'-(sec-butylperoxycarbonyl) benzophenone, 3,3 ', 4,4'-(t-butylperoxycarbonyl) benzophenone, 3,3 ', 4 , 4′−
Examples thereof include (laurylperoxycarbonyl) benzophenone, and among these, 3,3 ′, 4,4′-tetra (t-butylperoxycarbonyl) benzophenone is preferable. These compounds are used alone or in combination of two or more.

The compound (D) represented by the structural formula (I) may be used as it is, or may be used as a solution dissolved in an organic solvent such as toluene or xylene. The blending amount thereof is 0.01 to 20% by weight, preferably 0.5 to 10% by weight, based on the total amount [B or (B + C)] of the epoxy compound (A) of the present invention and the photopolymerizable compound.

In the present invention, as a photoinitiator, a compound other than the compound (D) represented by the structural formula (I) may be optionally contained in the magnetic coating material. Examples of such compounds include ketals such as benzyldimethyl ketal, benzoin methyl ether, benzoin ethyl ether, benzoin-i-propyl ether, benzoin, benzoins such as α-methylbenzoin, 9,10-anthraquinone, and 1 -Anthraquinones such as chloranthraquinone, 2-chloroanthraquinone and 2-ethylanthraquinone, benzophenone, p-chlorobenzophenone, p-
Benzophenones such as dimethylaminobenzophenone, 2-hydroxy-2-methylpropiophenone, 1
-(4-Isopropylphenyl) -2-hydroxy-2
-Propiofenones such as methylpropionenone,
Examples include suberones such as dibenzosuberone, sulfur-containing compounds such as diphenyldisulfide, tetramethylthiuram disulfide, and thioxanthone, and dyes such as methylene blue, eosin, and fluorescein, either alone or in combination of two or more. Then used.

In the present invention, the blending amount of the photoinitiator is 0 to 20% by weight, preferably 0.5 to 1 based on the total amount of the epoxy compound (A), the photopolymerizable compound and [B or (B + C)].
It is 0% by weight.

In the present invention, the addition of a reaction accelerator is effective when it is necessary to accelerate the reaction between the epoxy group and the carboxyl group. Examples of the reaction accelerator include 2-methylimidazole, 2-ethylimidazole, 2,4-dimethylimidazole, 2-ethyl-4-methylimidazole, 2
-Undecyl imidazole, 2-heptadecyl imidazole, 1-vinyl-2-methyl imidazole, 2-phenyl imidazole, 1-vinyl-2-ethyl imidazole, imidazole, 2-phenyl-4-methyl imidazole, 1-vinyl- 2,4-dimethylimidazole, 1-
Imidazoles such as vinyl-2-ethyl-4-methylimidazole, benzyldimethylamine, 2,4,6-tridimethylaminophenol, triethanolamine, triethylamine, N, N-dimethylpiperidine, α-methylbenzyldimethylamine, N-methylmorpholine, N,
Tertiary amines such as N-dimethylaminoethanol, N, N-diethylaminoethanol, N, N-dipropylaminoethanol and dimethylaminomethylphenol, and tertiary amines such as tridimethylaminomethylphenol triacetate and tribenzoate. There are salts and the like, which are used alone or in combination of two or more kinds.

In the present invention, the addition amount of these reaction accelerators is 0.05 to 5% by weight, preferably 0.1 to 5% by weight based on the total amount of the epoxy compound (A) and the photopolymerizable compound [B or (B + C)].
~ 3.5% by weight.

The fine powder magnetic particles (E) used in the present invention include Fe, γ
-Fe ₂ O _3, Co-containing _{γ-Fe 2 O 3, Fe} 3 O 4, Co -containing Fe ₃ O _4, cobalt ferrite _{(CoO · Fe 2 O 3)} , CrO 2, Co-Ni-p alloy, Co-N
i-Fe alloy, Co-Ni-Fe-B alloy, Fe-Ni-Zn alloy, Fe-Mn-Zn alloy, Fe-Co-Ni-p alloy, Ni-Co alloy, Fe-Ti-Si alloy, Fe -Co
-Si alloy, Fe-Ni alloy, Fe-Ag alloy, Fe-Cr-Co alloy, Fe-Cr
-Si alloy, Fe-Mn-Al alloy, barium ferrite (BaFe ₁₂ O
Known ferromagnetic fine powders such as ₁₉ ) are used.

The mixing ratio of the fine powder magnetic particles in the magnetic coating is 30 to 9
It is 0% by weight, preferably 50 to 85% by weight, more preferably 60 to 80% by weight.

The curable resin composition used as the binder of the present invention is easily manufactured by stirring and mixing at room temperature or under heating if necessary. Known thermal polymerization of hydroquinone, hydroquinone monomethyl ether, 1-butyl-catechol, p-benzoquinone, 2,5-t-butyl-hydroquinone, phenothiazine, etc. in order to prevent thermal polymerization during production or dark reaction during storage. It is desirable to add an inhibitor. The amount added is 0.001 with respect to the photopolymerizable compound of the present invention.
Is 0.1 to 0.1% by weight, preferably 0.001 to 0.05% by weight.

When it is necessary to adjust the viscosity of the magnetic coating material of the present invention, an organic solvent may be added and used.

Examples of usable organic solvents include alcohols such as methanol, ethanol, i-propanol, n-propanol and butanol, methyl acetate, ethyl acetate and acetic acid.
n-Butyl, ethyl lactate, esters such as glycol monoethyl ether acetate, acetone, methyl ethyl ketone, methyl isobutyl ketone, ketones such as cyclohexanone, ethyl ether, glycol dimethyl ether, glycol monoethyl ether, ethers such as dioxane, benzene, Aromatic hydrocarbons such as toluene and xylene, methylene chloride, ethylene chloride, carbon tetrachloride, chloroform, trichloroethylene,
Chlorinated hydrocarbons such as trichloroethane, perchloroethylene, chlorobenzene and dichlorobenzene, polar solvents such as dimethylformamide and dimethylsulfoxide can be used alone or in combination of two or more.

In the magnetic coating material of the present invention, if necessary, a plasticizer such as dibutyl phthalate, triphenyl phosphate, dioctyl sulfosodium succinate, t-butyl phenol-polyethylene ether, ethylnaphthalene-sulfonic acid sodium dilauryl succinate, stearin. It is also possible to add zinc acid, soybean oil lecithin, silicone oil, dispersants such as polyesters and polyurethanes containing sodium sulfonate groups, lubricants, lubricants and various antistatic agents.

The kneading machine used for the production of the magnetic coating material of the present invention is 2
There are a main roll mill, a three roll mill, a ball mill, a tron mill, a sand grinder, an attritor, a high speed impeller disperser, a high speed stone mill, a high speed impact mill, a desolver, a kneader, a high speed mixer, a homogenizer and an ultrasonic disperser.

The magnetic coating material of the present invention is applied onto a non-magnetic support, and its application method includes air doctor coat, blade coat, air knife coat, squeeze coat, roll choro, reverse co coat, impregnation coat,
Transfer roll coat, gravure coat, kiss roll coat, cast coat, spray coat,
Spin coat etc.

The shape of the support is not particularly limited as long as it is a non-magnetic support, but usually, a tape shape, a sheet shape, a disk shape,
Used in cards or drums.

Materials for the non-magnetic support include polyethylene terephthalate, polybutylene terephthalate, polyethylene, polypropylene, polybutadiene, polystyrene, polymethyl methacrylate, styrene-acrylonitrile copolymer, styrene-acrylonitrile-butadiene copolymer, cellulose triacetate, cellulose diacetate. , Cellulose acetate butyrate, cellulose acetate propionate, polyvinyl chloride, polyvinylidene chloride, polycarbonate, polyphenylene sulfide, polyamide, polyimide, polyamide imide and phenol resin, epoxy resin, unsaturated polyester resin,
Examples include plastics such as cured products of silicon resin, metals such as aluminum, copper, tin, zinc or non-magnetic alloys containing these, ceramics, glass and various papers. Among them, plastics and metals are suitable. This non-magnetic support is antistatic if necessary,
The back side may be back-coated for the purpose of preventing blocking, preventing transfer, and improving running performance.

When a solvent is added, the magnetic coating applied on the support is vaporized, and then a magnetic field is applied to orient the fine powder magnetic particles contained in the magnetic coating, followed immediately by an actinic ray such as an ultraviolet ray or an electron beam. And then completely cured by heat treatment.

Ultraviolet light sources used include high-pressure mercury lamps, low-pressure mercury lamps, ultra-high pressure mercury lamps, metal halide lamps, and electrodeless high-pressure mercury lamps. A photoinitiator is not always necessary when using an electron beam.

In the case of ultraviolet rays, the irradiation amount is generally required to be 100 mJ / cm ² or more as an integrated amount of ultraviolet rays, preferably 500 to
It is 5000 mJ / cm ² . The ambient temperature at the time of ultraviolet irradiation can be from room temperature to about 200 ° C., but when plastics or paper is used as the support, the temperature range from room temperature to 100 ° C. is preferable. The ultraviolet irradiation can be performed in the presence of air, but it is more effective if it is performed in the presence of an inert gas such as nitrogen gas, carbon gas or argon gas.

The heat treatment after irradiation with actinic rays is, for example, an ultraviolet heater,
Known methods such as hot air heating and high frequency heating are used. The heat treatment temperature can be arbitrarily selected according to the heat resistance of the support, but the temperature is generally 40 to 200 ° C., and the temperature of the plastics is preferably 40 to 100 ° C. in the case of papers. The heat treatment time is several minutes to several hours. The surface of the completely cured magnetic paint is generally smoothed.

The magnetic recording medium of the present invention can be used as various magnetic recording media such as magnetic tapes, video tapes, magnetic cards, magnetic tapes, floppy discs, magnetic hard discs and magneto-optical discs by taking advantage of the above advantages. You can

(Function) In the present invention, the compound (D) represented by the structural formula (I) is a photopolymerizable compound (B) having a carboxyl machine in the molecule or the compound (B) and another polymerizable compound (C). It is presumed that it significantly improves the curing by actinic rays such as ultraviolet rays and the complete curing by heating.

(Examples) The following examples will be given to more specifically describe the present invention, but of course the present invention is not limited to these examples.

In the examples, "parts" means "parts by weight". The performance measurements in the examples and comparative examples were according to other methods.

<Adhesion> According to a cross-cut / cellophane tape peeling test (JIS D-0202) of a hard coating of a magnetic paint.

<Hardness> According to the pencil hardness test (JIS D-0202) of the magnetic paint cured coating film.

Example 1. Epicoat 82, which is a bisphenol A type epoxy resin
8 (manufactured by "Yukaka Shell Co., Ltd."), 216 parts of monoacryloyloxyethyl succinate, 312 parts of tetrahydrofurfuryl acrylate, 100 parts of benzyl dimethyl ketal, N, N-diethylethanolamine 5
And 10 parts of a 25% by weight toluene solution of 3,3 ', 4,4'-tetra (t-butylperoxycarbonyl) benzophenone were stirred and mixed at room temperature to obtain a uniform transparent curable resin composition. 23 parts of this curable resin composition, γ-Fe ₂ O ₃ 7
When 5 parts, 2 parts of lecithin, 70 parts of cyclohexanone and 30 parts of toluene were placed in a glass bead type high-speed shaker and mixed for 1 hour, a magnetic coating material showing good dispersibility was obtained.

This magnetic paint was applied onto a 125 μ polyethylene terephthalate film using a reverse coat so that the solid content was 10 μm and dried at room temperature for 10 minutes, then 1000
Magnetic field orientation was carried out with an Elsted magnetic field. Then, after irradiation with 5.6 KW. Water-cooled high-pressure mercury lamp at 3000 mJ / cm ^2, it was heat-treated at 120 ° C. for 30 minutes to obtain a cured film of the magnetic paint.

The results of measuring the performance of the obtained cured coating film are shown in Table 1.

Example 2. Epicoat 1001, a bisphenol A type epoxy resin
(Manufactured by "Yuka Kaeru Co., Ltd.") 90 parts, monoacryloyloxyethyl succinate 43 parts, diacrylate 204 of 4 mol of bisphenol A ethylene oxide adduct
Parts, benzyl dimethyl ketal 100 parts, N, N-diethyl ethanolamine 10 parts and 3,3 ′, 4,4′-tetra (t-butylperoxycarbonyl) benzophenone 25 parts by weight toluene solution 10 parts at room temperature. By mixing, a uniform transparent curable resin composition was obtained. 25 parts of this curable resin composition, 70 parts of cobalt-coated γ-Fe ₂ O ₃ and lecithin 2
Parts and 100 parts of cyclohexanone were put in a glass bead type high-speed shaker and mixed for 1 hour to obtain a magnetic coating material showing good dispersibility. After coating and treatment in the same manner as in Example 1, ultraviolet irradiation was performed, and then heat treatment was performed.

Table 1 shows the measurement results of the performance of the obtained magnetic coating cured coating film.

Comparative Example 1. A magnetic paint cured coating film was obtained in the same manner as in Example 1 except that 3,3 ', 4,4'-tetra (t-butylperoxycarbonyl) benzophenone was not added. The results of measuring the performance of the obtained cured coating film are shown in Table 1.

Comparative Example 2. A magnetic paint cured coating film was obtained in the same manner as in Example 2 except that 3,3 ', 4,4'-tetra (t-butylperoxycarbonyl) benzophenone was not added. The results of measuring the performance of the obtained cured coating film are shown in Table 1.

Example 3. Epicoat 1001, a bisphenol A type epoxy resin
(Manufactured by "Yuka Kaeru") 90 parts, succinic acid mono-2-hydroxy-3-acryloyloxy-n-propyl ester 50 parts, bisphenol A ethylene oxide A mole adduct of 100 parts, benzyl dimethyl ketal 50 parts, N, N-diethylethanolamine 10
Parts and 3,3 ', 4,4'-tetra (t-butylperoxycarbonyl) benzophenone in a 25 wt% toluene solution 10 parts by stirring at room temperature to obtain a uniform transparent curable resin composition. 40 parts of this curable resin composition, γ-Fe ₂ O ₃ 60
Parts, 2 parts of lecithin, 180 parts of cyclohexanone and 40 parts of toluene were mixed by a glass bead type high-speed shaker for about 1 hour to obtain a magnetic paint having good dispersibility.

The resulting magnetic paint was dropped from a nozzle onto the aluminum substrate for a magnetic disk that had been previously diamond-ground,
After spin coating with a spinner at 0 rpm, the organic solvent was vaporized at 60 ° C. for 30 minutes, and then magnetic field orientation was carried out with a magnetic field of 1000 oersteds. Then 5.6KW. 3,500mj / cm ² after irradiation with a water-cooled high-pressure mercury lamp, 30 at 120 ° C.
Heat treatment was performed for minutes. The results of measuring the performance of the obtained cured coating film are shown in Table 1.

Comparative Example 3. A cured coating film of a magnetic coating material was obtained in the same manner as in Example 3 except that 3,3 ′, 4,4′-tetra (t-butylperoxycarbonyl) benzophenone was not added. The results of measuring the performance of the obtained cured coating film are shown in Table 1.

(Effect of the invention) In the present invention, by using the compound represented by the structural formula (I) as one component of the magnetic coating composition, the polymerization by the actinic radiation and the reaction by heating can be sufficiently performed, and the adhesion, A coating film having excellent hardness can be obtained.

Claims (1)

[Claims] 1. A magnetic recording medium comprising a non-magnetic support coated with a magnetic coating and cured, wherein the magnetic coating has an epoxy compound (A) having two or more epoxy groups in the molecule and a carboxyl group in the molecule. A photopolymerizable compound (B) or a mixture of the compound (B) with another photopolymerizable compound (C) and a curable resin composition containing the compound (D) represented by the structural formula (I). A magnetic recording medium, which is a magnetic coating material in which powder magnetic particles (E) are uniformly dispersed and contained. (However, R ₁ , R ₂ , R ₃ or R ₄ represents an alkyl group having 1 to 12 carbon atoms.)