JPS6098521A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve various performances such as adhesiveness, chemical resistance, durability, heat resistance and flexibility by using a curable type resin compsn. consisting of mixture composed of a photopolymerizable compd. having an epoxy compd. and a carboxylic group in a molecule and other photopolymerizable compd. and a photopolymn. initiator as a binder. CONSTITUTION:The curing of a curable resin compsn. to be used as a binder consists of two stages; first the reaction in which a photopolymerizable compd. B having a carboxyl group in the molecule or said compd. B and the other photopolymerizable compd. C are cured by irradiation of active rays to form a carboxyl group-contg. polymer then the reaction in which an epoxy compd. A reacts with the carboxyl group-contg. polymer and is thoroughly cured by heating. Diglycidyl ether of bisphenol A or the like is used for the epoxy compd. A and, for example, acrylic acid, methacrylic acid, etc. are used as the photopolymerizable compd. B. A compdn. having >=1 photopolymerizable double bonds in a molecule, for example, styrene, etc. are used for the photopolymerizable compd. C. The photopolymn. intiator includes benzyl dimethyl ketal, etc.

Description

Detailed Description of the Invention The present invention provides a magnetic recording medium in the form of a tape, sheet, card, drum, or disk in which a magnetizable layer in which finely powdered magnetic particles are dispersed in a binder is laminated, and is completely cured by heat treatment. It relates to magnetic recording media.

Conventionally, ethyl cellulose, nitrocellulose, polymethyl chlorochloride copolymer, polyurethane resin, epoxy resin, polyester resin, butadiene-acrylonitrile copolymer, etc. have been used as binders for magnetic recording media. Since the binder simply solidifies the resin component by evaporation of the solvent, it has the disadvantage that the adhesion of the magnetic recording layer is insufficient.

On the other hand, a method has been proposed in which an incyanate compound is added to the binder as a crosslinking agent to improve the adhesion to the support and physical properties (Japanese Patent Publication No. 47-28048), but these methods are Another drawback is that the pot life of magnetic paints is shortened due to the addition of compounds.

There is also a method of applying UV-curable cat fat as a binder, as described in JP-A No. 56-8468, but this method does not require a magnetic paint containing a large amount of finely powdered magnetic particles. It has a fatal flaw in that it cannot be completely cured due to insufficient penetration of ultraviolet rays.

Separately, Japanese Patent Publication No. 57-50801 describes a curing method using an electron beam using a radiation-polymerized resin as a binder, but this method not only requires significant equipment but also makes it difficult to control curing. However, there are drawbacks such as deterioration of the binder and support proceeding at the same time as curing.

In view of these circumstances, the present inventors have discovered that the pot life is long, the curing reaction can be easily controlled without any equipment problems, and, unlike conventional ultraviolet curable binders, the binder has a large fJl.
As a result of extensive research to find a new binder that can be completely cured despite containing fine powder magnetic particles, we have developed a photopolymerizable compound that contains an epoxy resin and a photopolymerizable compound that has a carboxyl group in the molecule. If a curable resin composition consisting of and a photosensitizer is used as a binder,
The inventors have discovered that the various deficiencies of the conventional binders described above can be solved and have arrived at the present invention.

That is, the present invention provides a curing method comprising a photopolymerizable compound (B) having at least two carboxyl groups in the molecule or a mixture of another photopolymerizable compound (C) and a photoinitiator. The present invention is a magnetic recording medium characterized by having a magnetizable layer comprising a resin composition containing finely powdered magnetic particles uniformly dispersed therein.

To cure the curable resin composition used as the binder of the present invention, first, a photopolymerizable compound Ct3) having a carboxyl group in the molecule or the compound (B) and another photopolymerizable compound (C) are exposed to active light. This process consists of two steps: curing by irradiation to form a carboxyl group-containing polymer, and then heating to completely cure the epoxy compound by reacting with the carboxyl group-containing polymer. Such a curing reaction is essentially a different curing method from the conventional curing reaction using only ultraviolet rays or the curing reaction using a combination of ultraviolet curing and thermal curing reaction using an organic peroxide.

The completely cured product obtained from the curable resin composition used as the binder of the present invention has excellent properties such as adhesion, chemical resistance, water resistance, heat resistance, and flexibility. As a composition, it has the great advantage of being excellent in storage stability.

Curable resin compositions that combine an epoxy compound and a photopolymerizable compound are photocurable or thermosetting resin compositions that provide cured products with excellent performance such as flexibility, heat resistance, and adhesiveness. Proposals have been made regarding this. for example,
A curable resin composition containing amines has been proposed in JP-A-51-101. This composition is a thermosetting resin composition that utilizes a reaction and is said to cure at low temperatures and produce a relatively flexible cured product, and uses polyamines having primary or secondary amine groups. Therefore, it has the disadvantage of extremely poor storage stability.

Further, in Japanese Patent Publication FIi'357-13572, polyvalent (methacrylate) (meaning acrylate and methacrylate. Hereinafter, the same abbreviation), an epoxy compound, and a phosphoric acid having a polymerizable unsaturated bond are described. Photocurable resin compositions containing esters have been proposed. Although it is stated that a cured product with good performance such as flexibility and adhesion can be obtained from this composition, the drawback is that the cured product has significantly poor water resistance because it uses a phosphoric acid ester. have. As described above, there have been some proposals for combining epoxy compounds and (meth)acrylate compounds, but as mentioned above, all of them have serious drawbacks.

The epoxy compound (A) having at least two epoxy groups in the molecule, which is an essential component of the curable resin composition used as a binder in the present invention, refers to an epoxy compound having two or more epoxy groups in one molecule. and its evogishi it is 100 to 4,000, preferably 100 to 4,000
i, o o o.

Typical compounds include bisphenol type epoxy resins which are diglycidyl ethers such as bisphenol A, bisphenol F1 and tetragenated bisphenol A, and novolak type epoxy resins which are polyglycidyl ethers such as phenol novolak and cresol novolak. Polyglycidyl ethers of dihydric or higher polyhydric phenols, polyhydric alcohols with dihydric or higher hydrides such as ethylene glycol, propylene glycol, neopentyl glycol, polyhydric acid, 4-butanediol, 1,6-hexanediol, trimethylolpropane, etc. Novoliglycidyl ethers, phthalic acid, isophthalic acid, tetrahydro7
Polyglycidyl esters of divalent or higher polyhydric carbonic acids such as talic acid, hexahydrophthalic acid, and adipic acid;
Polyglycidyl ethers in which the active hydrogen bonded to the nitrogen atom of aniline, isocyanuric acid, etc. is replaced with a glycidyl group, vinylcyclohexene dieboxide obtained by epoxidizing the olefin bond in the molecule, 3,4-epoxycyclohexylmethyl -3,4-epoxycyclohexanecarboxylate, 2-(3,4-epoxy)cyclohexyl-5,5-spiro(3,4,-epoxy)
Alicyclic polyepoxy compounds such as cyclohexane-m-dioxane; Examples include aminopolyepoxy compounds such as methyl)cyclohexane.

These epoxy compounds can be used alone or in combination of two or more.

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

Among these epoxy compounds having at least two epoxy groups in the molecule, preferred epoxy compounds include diglycidyl ether of bisphenol A, phenol novolac type polyepoxy compounds, talesol novolak type polyepoxy compounds, and polyhydric alcohol polyepoxy compounds. Examples include epoxy compounds.

The essential components of the curable resin composition used as the binder of the present invention include one or more unsaturated carboxylic acid compounds such as dicaric acid, tetratonic acid, and fumaric acid, and (11
) There is a compound represented by the following general formula (I).

1 (CM, = C-COOYiR, tA→R,)-(CO
OH)n ・=(I) (wherein, R represents hydrogen or a methyl group, R1 represents an aliphatic, aromatic, or alicyclic residue, respectively, A represents an ester bond, m and n each represent a positive integer of 1 to 3.) In the general formula (I), R1 is a divalent to tetravalent hydrocarbon group having 2 to 10 carbon atoms or a hydroxy/I/group-containing hydrocarbon group. It is preferable that R1 has 2 carbon atoms.
-10 divalent aliphatic polybasic acid residue, divalent to tetravalent aromatic polybasic acid residue having 6 to 15 carbon atoms, or divalent to tetravalent aromatic polybasic acid residue having 6 to 10 carbon atoms is preferably an alicyclic polybasic acid residue.

There are the following compounds.

Examples of the compound where m=1 and n=1 include cobalic acid mono(meth)acryloyloxyethyl ester, phthalic acid mono(meth)acryloyloxyethyl ester,
Maleic acid mono(meth)acryloyloxyethyl ester, tetrahydroheptalic acid mono(meth)acryloyloxyethyl ester, hexahydrophthalic acid mono(meth)acryloyloxyethyl ester, endo-
Bisic0(2.2.1)-5-hebutene-2,3-dicarboxylic acid mono(meth)acryloyloxyethyl ester, tetrahydroheptatalic acid mono-2-(meth)acryloyloxy-1-(phenoxymethyl ) Ethyl ester, phthalic acid mono-2-hydroxy-3-(meth)acryloyloxypropyl ester, succinic acid mono-2-
Examples include hydroxy-3-(meth)acryloyloxypropyl ester.

Examples of the compound where m=1 and n÷2 include tridiethyl ester.

Examples of the compound where m=1 and n=3 include pyromellitic acid mono-2-(meth)acryloyloxyethyl ester.

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

Examples of compounds where m=2 and n=2 include trimellitic acid mono-[4,5-bis(meth)acryloyloxyneopentyl] ester, trimellitic acid mono-(3,
Examples include 4-bis(meth)acryloyl A/oxyisobutyl ester.

Examples of the compound where m=3 and n=2 include trimellitic acid mono-(3,4,5-)lis(meth)acryloyloxyneopentyl] ester.

Examples of the compound where m=3 and n=3 include pyromellitic acid mono-[3,4,5-)lith(meth)acryloyloxyneopentyl]ester.

Among the above-mentioned compounds, as the photopolymerizable compound (B),
Particularly preferred is (11). These photopolymerizable compounds ω) having a carboxyl group in the molecule may be used alone or in combination of two or more, or in combination with one or more of the other photopolymerizable compounds C) described below. Ru.

The amount of the photopolymerizable compound (J3) containing one or more carboxyl groups in the molecule in the photopolymerizable compound (B1C) used in the present invention is 10 to 100% by weight.

If the amount is less than 10% by weight, the resulting cured product will have insufficient properties such as adhesiveness, water resistance, and heat resistance.

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

Examples of photopolymerizable compounds having one photopolymerizable double bond in the molecule include (1) styrenic compounds such as styrene, α-methylstyrene, and chlorostyrene;
(iD methyl (meth)acrylate, ethyl (meth)acrylate, n- and l-propyl (meth)acrylate, n-, Bee- and t-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, ) acrylate, alkyl (meth)acrylates such as stearyl (meth)acrylate, alkoxyalkyl (meth)acrylates such as methoxyethyl (meth)acrylate, ethoxyethyl (meth)acrylate, butoxyethyl (meth)acrylate,
Alitetraxyalkyl (meth)acrylates such as phenoxyethyl (meth)acrylate; hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate;
meth)acrylates, hapgen-substituted alkyl(meth)
Acrylates, or polyoxyalkylene glycol mono(meth)acrylates such as polyethylene glycol mono(meth)acrylate, polypropylene glycol mono(meth)acrylate, or substituted alkyl mono(meth)acrylates such as alkoxypolyoxylalkylene mono(meth)acrylate (iii) mono(meth)acrylates of alkylene oxide adducts of bisphenol A, such as ethylene oxide and propylene oxide adducts of bisphenols, hydrogen mono(meth)acrylates of alkylene oxide adducts of hydrogenated bisphenol A, such as ethylene oxide and propylene oxide adducts of hydrogenated bisphenol A; One (meth)acrylate in the molecule obtained by further reacting a terminal isocyanate group-containing compound with an alcoholic hydroxyl group-containing (meth)acrylate.
Urethane-modified mono(meth)acrylates having an acrytetrayloxy group, (V) 1 m JJ in the molecule, Epoxy mono(meth) obtained by reacting the above compound having an epoxy group with acrylic acid or methacrylic acid Acrylates and (vt) oligoester mono(meth)acrylates obtained by reacting acrylic acid or methacrylic acid or polyhydric carboxylic acid as a carboxylic acid component with a polyhydric alcohol of divalent or higher valence as an alcohol component, etc. .

Examples of photopolymerizable compounds having two photopolymerizable double bonds in the molecule include (1) ethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, and 1,4-butane. Giorgi (meta)°
r Acrylate Alkylene glycol di(meth)acrylates such as neopentyl glycol di(meth)acrylate, 1,6-hexanethiol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethyleneglyfur di(meth)acrylate , polyoxyalkylene glycol di(meth)acrylates such as dibutetrabylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, halogen-substituted alkylene glycol di(meth)acrylates H1-substituted alkylene glycol di(meth)acrylates such as ethylene oxide and propylene oxide adducts of (+D bisphenol A);
-/l/A di(meth)acrylate-11 of alkylene oxide adducts, di(meth)acryle-11 of alkylene oxide adducts of hydrated bisphenol A such as ethylene oxide and propylene oxide adducts of hydrated bisphenol A acrylates, (iii) diisocyanate compound and 2
Two (meth)acryloyloxy molecules are obtained by further reacting a terminal incyanate group-containing compound obtained by preliminarily reacting two or more alcoholic hydroxyl group-containing compounds with an alcoholic hydroxyl group-containing (meth)acrylate. urethane-modified di(meth)acrylates having a group, (iv) an epoxy di(meth)acrylate obtained by reacting a compound niacrylic acid or /δ and methacrylic acid having two or more epoxy groups in the molecule, (v) )
Examples include oligoester di(meth)acrylates obtained by reacting acrylic acid or methacrylic acid and polyhydric carboxylic acids as the carboxylic acid component with polyhydric alcohols of dihydrity or more as the alcohol component.

Examples of photopolymerizable compounds having three or more photopolymerizable double bonds in the molecule include (+) IJ methylolepropane tri(meth)acrylate, trimethylolethane tri(meth)acrylate, and pentaerythritol. Poly(meth)acrylates of trihydric or higher aliphatic polyhydric alcohols such as tetra(meth)acrylate, poly(meth)acrylates of trivalent or higher halogen-substituted aliphatic polyhydric alcohols, (11) diisocyanate compound and 3 A terminal isocyanate group-containing compound obtained by reacting a compound containing an alcoholic hydroxyl group in advance with a (meth)acrylate containing an alcoholic hydroxyl group has three or more (meth)acryl groups in the molecule. urethane-modified poly(meth)acrylates having groups, epoxy poly(meth)acrylates obtained by reacting acrylic acid or/and methacrylic acid with a compound having three or more epoxy groups in the liD molecule, etc. .

Epoxy compound (5) contained in the binder of the present invention
The blending ratio of the photopolymerizable compound I#JΦ) or ω) having a carboxyl group in the molecule and the mixture of the other photopolymerizable compound (C) is epoxy compound (A):photopolymerizable compound [ ) or ω) + (c)] = z o : 90
~90:10 (weight ratio), preferably epoxy compound: photopolymerizable compound [ω) or CB)+
(C)]=2o:so to 80:20 (heavy h1 ratio). The amount of epoxy compound (A) is 10% by weight and 7%
If it is less than that, the reaction between the photopolymerizable compound CB) having a carboxyl group in the molecule and the epoxy compound (a) is substantially too small, making it difficult to obtain a cured product with excellent adhesiveness, heat resistance, etc.

The photoinitiator used in the present invention is a compound that promotes the photopolymerization reaction of a photopolymerizable compound, and includes, for example, ketals such as benzyl dimethyl ketal, benzoin methyl ether, benzoin ethyl ether, benzoin-1 - Benzoins such as propyl ether, benzoin, and α-methylbenzoin; 9. io-anthraquinone, 1-ri tetraanthraquinone, 2-ri p-anthraquinone, 2-
Anthraquinones such as ethyl anthraquinone, benzophenones such as benzophenone, p-chlorobenzophenone, p-dimethylaminobenzophenone, 2-hydroxy-2-methylpropiophenone, 1-(4-isoprohylphenyl)-2-hydroxyr2- Examples include propiophenones such as methylpropiophenone, suberones such as dibenzosuberone, sulfur-containing compounds such as diphenyl disulfide, tetramethylthiuram disulfide, and thioxanthone, and pigments such as methylene blue, eosin, and fluorescein. or in combination of two or more.

In the present invention, the blending amount of this photoinitiator is 0.05 to 0.05 to the total amount of the epoxy compound (4) and the photopolymerizable compound.
The amount is 20% by weight, preferably 0.5 to 10% by weight.

In the present invention, when it is necessary to promote the reaction between an epoxy group and a carboxyl group, it is effective to add a reaction promoter. Examples of the reaction accelerator include 2-methylimidazole, 2-ethylimidazole, 2,4-dimethylimidazole, 2-ethyl-4-methylimidazole,
2-Undecylimidazole, 2-heptadecylimidazole, 1-vinyl-2-methylimidazole, 2-phenylimidazole, 1-vinyl-2-ethylimidazole, imidazole, 2-phenyl-4-methylimidazole, 1-vinyl- 2,4-dimethylimidazole,
Imidazoles such as 1-vinyl-2-ethyl-4-methylimidazole, benzyldimethylamine, 2,4.
6-) Lydimethylaminophenol, triethanolamine, triethylamine, N,N'-dimethylpiperidine, α-methylbenzyldimethylamine, N-methylmorpholine, N,N-dimethylaminoethanol,
These include tertiary amines such as N,N-diethylaminoethanol, NlN-dipropylaminoethanol, and dimethylaminomethylphenol, and tertiary amine salts such as triacetate and tribenzoate of tridimethylaminomethylphenol. Two or more types are used in combination.

In the present invention, the addition amount of these reaction accelerators is O, O
S to 5% by weight, preferably 0.1 to 3.5% by weight
It is.

The curable resin composition used as the binder of the present invention is easily produced by stirring and mixing at room temperature or under heating if necessary. In order to prevent thermal polymerization during production and darkness window during storage, known compounds such as hydroquinone, hydrotetraquinone monomethyl ether, 1-butyl-catefur, p-benzoquinone, 2°5t-butyl-hydroquinone, and fetchacin are used. It is desirable to add a thermal polymerization inhibitor. The amount added is 0.0% relative to the photopolymerizable compound of the present invention.
001 to 0.1% by weight, preferably 0.001 to 0.1% by weight
It is a 0.05 heavy view.

The fine powder magnetic particles used in the present invention include s
FeSγ-Fe, O,, Co-containing 7-Fe, O,, F
e, O, C.

Contains Fe, O, ”pardo aerite (Co o ・
Fe+Os), Cry, Co-Ni-p alloy, C
o -Nl-Fe alloy\Co--5t alloy, Fe-c
o -Si alloy, Fe-Ni alloy, Fe-Ag alloy,
Fe-Cr-Co alloy, Fe-Cr-Si alloy,
Known ferromagnetic fine powders such as Fe-Mll-A1 alloy can be used.

The blending ratio of the fine powder magnetic particles in the magnetic paint consisting of the fine powder magnetic particles and the binder is 30 to 90% by weight, 50 to 85% by weight, and preferably 60 to 80% by weight.

The curable resin composition used as a binder in the present invention can be used as it is or mixed with finely powdered magnetic particles, but if viscosity adjustment is required, it may be mixed with tanol, i-propatool, n-pro/propylene, etc. Alcohols such as alcohol and butanol, methyl acetate, ethyl acetate, n-butyl acetate,
Esters such as ethyl lactate and acetic acid glycol monoethyl ether; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; ethers of ethyl ether, glycol dimethyl ether, glycol monoethyl ether, and dioxannat;
Aromatic hydrocarbons such as benzene, toluene, and xylene; chlorinated hydrocarbons such as methylene chloride, ethylene chloride, carbon tetrachloride, chloroform, trichloroethylene, trichloroethane, perchlorethylene, chlorobenzene, and dichlorobenzene; dimethylformamide; Polar solvents such as dimethyl sulfoxide can be used alone or in combination of two or more.

The magnetic paint of the present invention may optionally contain plasticizers such as dibutyl phthalate and triphenyl phosphate, dioctyl sulfonodium succinate, t-butylphenol-polyethylene ether, ethylnaphthalene-sulfonic acid sodium dilauryl succinate, and zinc stearate. It is also possible to add lubricants such as soybean oil lecithin, silicone oil, polyester or polyurethane containing sodium sulfonate groups, and various antistatic agents.

In the present invention, the cross-mixing machine used for cross-dispersing the binder and fine powder magnetic particles includes a two-roll mill, a three-roll mill, a ball mill, a tron mill, a sand grinder, an attritor, a high-speed impeller dispersion machine, a high-speed stone mill, and a high-speed impact mill. There are mills, desolvers, kneader-1 high-speed mixers, homogenizers, ultrasonic dispersers, etc.

To form the magnetic recording layer in the present invention, finely powdered magnetic particles are mixed and dispersed in a binder, or the organic solvent described above is further added thereto, and then coated on a nonmagnetic support. Application methods include air doctor coat,
Blade coat, air knife coat, squeeze coat, roll coat, reverse coat, impregnation coat,
There are transfer roll coats, gravure coats, kiss roll coats, thousands of coats, spray coats, and spin coats.

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

Materials for the non-magnetic support include polyethylene terephthalate, polybutylene terephthalate-polyethylene, polypropylene, polybutadiene, polystyrene, polymethyl methacrylate, styrene-acrylic hair tolyl copolymer, styrene-acrylic t=+1) lylubutadiene copolymer, Cellulose triacetate, cellulose diacetate, cellulose acetate butyrate, cellulose acetate propionate, polyvinyl chloride, polyvinylidene chloride, polycarbonate, polyphenylene sulfide, polyamide, polyimide, polyamideimide, phenolic resin, epoxy resin, unsaturated polyester resin, silicone Examples include plastics such as cured resins, metals such as aluminum, copper, tin, zinc or non-magnetic alloys containing these, ceramics, glass, and various papers. Among them, plastic and gold8 are suitable.
It is class 6. This non-magnetic support may be coated with a back coating on the mirror surface, if necessary, for purposes such as anti-static, anti-bucking, anti-transfer, and improved runnability.

If a solvent is added to the magnetic paint coated on the support, the solvent is vaporized, a magnetic field is applied to orient the fine powder magnetic particles contained therein, and then actinic rays such as ultraviolet rays or electron beams are immediately irradiated. Then, it is completely cured by heat treatment.

The ultraviolet light sources used include high-pressure mercury lamps, low-pressure mercury lamps, ultra-high-pressure mercury lamps, metal/%ride lamps, and electrodeless high-pressure mercury lamps. When using an electron beam, a light starting side is not necessarily required.

In the case of ultraviolet rays, the irradiation amount generally requires an integrated ultraviolet value of toomj/ff1 or more, preferably 50
It is 0 to 5000 mj/ct/i. The ambient temperature during ultraviolet irradiation can range from room temperature to about 200°C, but when using plastics or paper as a support, the temperature ranges from room temperature to 10°C.
Temperature ranges up to 0°C are preferred. Although ultraviolet irradiation is possible in the presence of air, it is more effective when carried out in the presence of an inert gas such as nitrogen gas, charcoal, gas, or argon gas.

For the heat treatment after irradiation with actinic rays, known methods such as infrared heater, hot air heating, and high frequency heating may be used. The heat treatment temperature can be arbitrarily selected depending on the heat resistance of the support, but generally the temperature is 40 to 200°C, and in the case of plastics and papers, the temperature is preferably 40 to 100°C. The nfJ during the heat treatment is several minutes to several hours. The surface of a completely cured magnetic paint is generally smoothed.

As mentioned above, the curable resin composition used as a binder in the present invention is different from conventional ultraviolet curable resin compositions and ultraviolet thermosetting resin compositions that combine ultraviolet curing and heat curing with organic harsh substances. The curing reaction is essentially different, and magnetic coatings using the curable resin composition as a binder have excellent properties such as adhesion to the support used, water resistance, heat resistance, and flexibility for magnetic recording media. can be obtained.

In the present invention, the following points can be mentioned as effects depending on the curable resin composition used as a binder for 2 hours.

1) The compatibility of the epoxy compound GJ (A) and the photopolymerizable compound [ω) or a mixture of ω) and (C)] is excellent at 8t, and the viscosity of the magnetic paint can be adjusted freely, and it can be adjusted as needed. It is also possible to reduce the viscosity significantly.

2) Excellent adhesion to the magnetic paint support.

3) Rapid curing is possible by actinic light curing, and the orientation of fine powder magnetic particles can be immediately fixed, which is particularly advantageous for vertical arsenization.

4) Actinic light-curable resins can completely cure extremely thick coatings.

By taking advantage of the above-mentioned advantages, the magnetic recording medium of the present invention can be used as a variety of magnetic recording media such as magnetic tape, video recording medium, magnetic card, magnetic ticket, floppy disk, magnetic hard disk, magneto-optical disk, etc. It can be said that its industrial significance is extremely large.

Examples will be given below to explain the present invention more specifically, but the present invention is of course not limited by the Examples.

In the examples, parts simply indicate parts by weight.

Example 1 Epicote 82, a bisphenol A epoxy resin
8 (manufactured by Yuka Shell Chemical Co., Ltd.), 216 m of succinic acid monoacryloyloxyethyl ester, 312 parts of tetrahydrofurfuryl acrylate, 100 parts of benzyl dimethyl ketal, and 5 parts of N,N-diethylethanolamine were mixed with stirring at room temperature. A uniform transparent curable resin composition was obtained. 23 parts of this curable resin composition, γ-Fe,
When 0.75 parts of lecithin, 2 parts of lecithin, and 100 parts of cyclohexanon were placed in a glass bead type high-speed shaker and mixed for 1 hour, a magnetic paint exhibiting good dispersibility was obtained.

This magnetic paint was applied onto a 125μ polyethylene terephthalate film using a reverse coater, and
After drying for minutes, magnetic field orientation was performed using a magnetic field of 1000 oersteds. Then, it was calendered for 9 hours in a 100℃ super calendar, and then heated for 3000 hours in a 5.6KW water-cooled high-pressure mercury lamp.
After rnJ/tJ irradiation, heat treatment was performed at 120°C for 30 minutes. When the adhesion of the magnetic paint was measured by a cross-cut tape peel test, a good result of 100/100 was obtained.

Example 2 Epicor) 10 which is a bisphenol A type epoxy resin
01 (manufactured by Yuka Shell Chemical Co., Ltd.), 43 parts of succinic acid monoacryloyloxyethyl ester, and 10 parts of bisphenol A ethylene oxide (4 moles) amine were stirred and mixed at room temperature to obtain a uniform transparent curable resin composition. 25 parts of this curable resin composition, cobalt-coated γ-Fe, 0.70
1 part, 2 parts of lecithin, and 100 parts of cyclohexanone were placed in a glass bead type high-speed shaker and mixed for 1 hour. A magnetic paint exhibiting good dispersibility was obtained.

The fabric was laundered in the same manner as in Example 1, treated, irradiated with ultraviolet rays, and then subjected to heat treatment. The adhesion of the magnetic paint was measured using a p-scut tape peel test, and a good result of 100/100 was obtained.

Comparative Example 1 A magnetic recording medium was obtained in the same manner as in Example 1 except that the heat treatment after ultraviolet irradiation was not performed. The adhesion of magnetic paint was measured using a cross-cut tape peel test and was 0/Zoo.
It was defective.

Comparative Example 2 A magnetic recording medium was obtained in the same manner as in Example 2, except that the heat treatment after irradiation with ultraviolet rays was not performed. The adhesion of the magnetic paint was 0/100 as measured by a cross-cut tape peel test.
It was defective.

Comparative Example 3 A magnetic recording medium was obtained in the same manner as in Example 1 except that the ultraviolet irradiation in Example 1 was not performed. The adhesion of the magnetic paint was determined by a cross-cut tape peel test and was poor at O/100.

Comparative Example 4 A magnetic recording medium was obtained in the same manner as in Example 2 except that the ultraviolet irradiation in Example 2 was not performed. The adhesion of the illumination material was determined by a cross-cut tape peeling test and was poor at O/100.

Example 3 Epicote 10, a bisphenol A epoxy resin
01 (manufactured by Yuka Shell Chemical Co., Ltd.) 90 parts, succinic acid mono 2
- 50 parts of hydroxy-3-acryloyloxypropyl ester, 100 parts of diacrylate of 4 mol adduct of bisphenol artificial tylene oxide, 50 parts of benzyl dimethyl ketal and 10 parts of N,N-diethylethanolamine were mixed with stirring at ￥ temperature. A uniform transparent cured composition was obtained. 40 parts of this curable resin composition, γ-Fe, 0.6
0 parts, 2 parts of lecithin, and 180 parts of cyclohexanone were mixed for about 1 hour using a glass bead type high-speed shaker.
A magnetic paint exhibiting good dispersibility was obtained.

The obtained magnetic paint was dropped from a nozzle onto an aluminum substrate for a magnetic disk that had been diamond ground in advance, and 3.
After spin coating was performed using a spinner at 000 rpm, the organic solvent was vaporized at 60° C. for 30 minutes, and then magnetic field orientation was performed using a magnetic field of 1000 oersted. Then 3,500 IJ with 5.6 parts w water-cooled high pressure mercury lamp.
/ cnl irradiation, heat treatment was performed at 120° C. for 30 minutes. The hard adhesion of the magnetic paint was measured by a cross-cut tape peel test, and a good 7J result of 100/100 was obtained.

Special story: Toyobo Co., Ltd.

Claims (1)

[Claims] (1) An epoxy compound (A) having at least two epoxy groups in the molecule and a photopolymerizable compound having a carboxyl group in the molecule) or the compound (B) and another photopolymerizable compound (C) Finely powdered magnetic particles are uniformly dispersed in a curable resin composition consisting of a mixture of and a photoinitiator.
1. A magnetic recording medium comprising a magnetizable layer containing: