JPS62219229A - Magnetic recording medium curable by radiation - Google Patents

Abstract

PURPOSE:To improve the stability of a magnetic coating compd., squareness ratio and smoothness by using a resin curable by radiation which has at least one acrylic double bond in the molecule and is formed by bringing at least one kind among specific phosphorus compds. and compd. contg. a hydrophilic group except phosphorus into reaction as a component of a binder. CONSTITUTION:This recording medium is formed by using the resin curable by radiation which has at least one acrylic double bond in the molecule and is formed by bringing at least one kind among the phosphorus compds. expressed by the formulas I-IV and the compd. contg. the hydrophilic group except phosphorus into reaction as the component of the binder. In the formulas, X, Y denote an ester formable functional group, R1 denotes an alkyl group, etc., of 1-12 C, R3, R4 denote an alkylene group, etc., of 3-10 C, m denotes an optional numerical value among 1-4, M denotes an alkali metal atom, etc. The constitutional formulas of the representative examples for the phosphorus compds. are exemplified by the formula I-1- the formula V-1.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a radiation-curable magnetic recording medium with excellent magnetic and mechanical properties.

(Prior art) General-purpose magnetic tape is made by dispersing acicular magnetic particles with a long axis of 1 μm or less in a binder solution with appropriate additives (dispersants, lubricants, antistatic agents, etc.) to create a magnetic coating. It is made by coating polyethylene terephthalate film.

Magnetic recording media are required to have high magnetic recording density and high reproduction output, and for this purpose, it is necessary to highly fill and highly align magnetic particles with high coercive force. In order to achieve high filling and high orientation, the magnetic particles must be dispersed down to the primary particles. The dispersion of magnetic particles is greatly influenced by the binder, and no matter how efficient a dispersion machine is used, if the binder's dispersibility is low, the magnetic particles will not be dispersed in the paint. Furthermore, although magnetic particles with high coercive force have been developed, as the coercive force increases, the magnetic particles become more difficult to disperse.

Traditionally, binders for magnetic paints include vinyl chloride/vinyl acetate copolymer, vinyl chloride/vinyl acetate/vinyl alcohol copolymer, vinyl chloride/vinylidene chloride copolymer, thermoplastic polyurethane resin, thermosetting polyurethane resin, and polyester. Resin, acrylonitrile-butadiene copolymer, nitrocellulose, cellulose e-acetate,
Butyrate, epoxy resin, acrylic resin, etc. are used. On the other hand, as radiation-curable binders, vinyl chloride/vinyl acetate copolymers with acrylic double bonds, synthetic resins, polyester resins, polyurethane resins, acrylic resins, etc. have been proposed; Currently, the magnetic properties are not sufficient for applications that require high performance, such as computer tapes. It is known that surfactants are used as dispersants to improve magnetic properties, but the presence of low molecular weight surfactants in magnetic coatings has the disadvantage of deterioration of physical properties and changes over time. be.

Magnetic tape not only has excellent magnetic properties, but also wear resistance,
It must have excellent mechanical properties such as runnability, flexibility, and adhesion to the support. Magnetic tapes using polyester resins and polyurethane resins as binders are disclosed in Japanese Patent Publication No. 17947-1970 and Japanese Patent Publication No. 18222-1973.
Special Publication Showa 45-24900゜Special Publication Showa 44-23500.
Special Publication No. 45-24902, Special Publication No. 49-48126,
Special Publication No. 48-31611, Special Publication No. 48-31610.
As seen in Japanese Patent Publication Nos. 42-15432 and 51-6522, it has excellent mechanical properties and is a useful material as a magnetic tape binder.

(Problems to be Solved by the Invention) It has been disclosed in JP-A-54-28603 and JP-A-54-28603 that the dispersibility of magnetic particles is dramatically improved by introducing a metal salt of sulfonic acid into polyester resin or polyurethane resin. 1972-
As disclosed in Japanese Patent No. 157603, the effect of metal salts of sulfonic acid is due to its hydrophilicity, and metal salts of phosphorus compounds such as phosphinic acid and phosphonic acid can also be expected to have similar effects, and furthermore, they are effective against radiation. Similar effects can be expected with curable resins. However, metal salts of phosphorus compounds such as phosphinic acid and phosphonic acid may cause deactivation of the catalyst during the production of polyester resins, polyurethane resins, polyester acrylate resins, acrylate compounds, etc., or the physical properties of the resulting polymer due to the formation of ether bonds. or because they have different polarities, they may separate without reacting uniformly.

Even in polyurethane resins, polyurethane acrylate resins, epoxy acrylate resins, etc., metal salts of phosphorus compounds such as phosphinic acid and phosphonic acid are highly inorganic, so they can be reacted in a general-purpose solvent or without a solvent to form hydrophilic groups in the resin. It was impossible to introduce

(Means to Solve the Problem) In view of the above circumstances, the inventors of the present invention aimed to improve the dispersibility of magnetic particles while the cured coating film retains the mechanical properties of polyester resin and polyurethane resin. As a result of intensive studies with the aim of improving the properties of magnetic particles, we have found that by using a specific phosphorus compound, stable production of polyurethane acrylate resin is possible, and the desired dispersibility of magnetic particles can be significantly improved. I found it.

That is, the present invention provides a magnetic recording medium in which a magnetic material in which ferromagnetic powder is dispersed in a binder is coated on a non-magnetic support and cured by radiation, which has at least one acrylic double bond in the molecule, and which has the following: A radiation curable resin obtained by reacting at least one phosphorus compound represented by formulas (1) to (to) with a hydrophilic polar group-containing compound other than phosphorus as a component of the binder. It is a curable magnetic recording medium.

OM 0M Cx+y is an ester-forming functional group, R1 has 3 to 1 carbon atoms
0 trivalent hydrocarbon group, R2 is an alkyl group having 1 to 12 carbon atoms, a cycloalkyl group, an aryol group, and 1 to 12 carbon atoms.
represents an alkoxy group, a cycloalkoxy group, or an aryoloxy group. The aryl group and the aryloxy group may have a halogen atom, a hydroxy group, -0M'(M' represents an alkali metal), or an amino group bonded thereto. R,, R4 is an alkylene group having 1 to 12 carbon atoms, a cycloalkylene group, an arylene group, or a group of the following formula (CH2-
ORs, a group represented by t (Rs represents an alkylene group having 1 to 12 carbon atoms, a cycloalkylene group, or an arylene group);

m can take any value from 1 to 4. M represents an alkali metal atom, hydrogen, a monovalent hydrocarbon group, or an amino group. ] The radiation-curable resin of the present invention has at least one acrylic double bond in the molecule, at least one of the phosphorus compounds shown in formulas (1) to (to) above, and a hydrophilic compound other than the phosphorus atom. This is a phosphorus-containing radiation-curable resin that has been reacted with a polar group-containing compound. Specifically, acrylic double bond-containing compounds (
8) and a resin bonded through at least one type of bond among urethane bonds, ester bonds, ether bonds, and amide bonds, such as polyurethane acrylate resins, polyester acrylate resins, epoxy acrylate resins, various acrylate compounds, etc. Can be mentioned.

Refers to a residue (acryloyl group or methacryloyl group) of acrylic double bond methacrylic acid amide, etc. contained in the binder of the present invention.

The acrylic double bond-containing compound (2) is (meth)
Carboxyl group-containing acrylic compounds (A-1) such as acrylic acid, glycol monomers (A-1) such as ethylene glycol, diethylene glycol, hexamethylene glycol, etc.
Mono(meth)acrylates and di(meth)acrylates of triol compounds such as meth)acrylate, trimethylolpropane, glycerin, and trimethylolethane, mono(meth)acrylates of polyols with 4 or more valences such as pentaerythritol and dipentaerythritol, Hydroxyl group-containing acrylic compounds such as di(meth)acrylate, tri(meth)acrylate, glycerin monoallyl ether, glycerin diallyl ether (A-2
), glycidyl group-containing acrylic compounds (A-3) such as glycidyl (meth)acrylate, amine group-containing acrylic compounds (A-4) such as (meth)acrylamide, monomethylol (meth)acrylamide, cyanethyl (meth) ) Isocyanate group-containing acrylic compounds (A-5) such as acrylate.

At least one of these acrylic double bonds must exist in the molecule of the binder. If the number is less than one, the crosslinking density will not be sufficiently high, resulting in a film with poor mechanical strength, which is not preferable.

A polyurethane acrylate resin is generally obtained by reacting a hydroxyl group-containing resin and a hydroxyl group-containing acrylic compound (A-2) with a polyisocyanate-containing compound.

Hydroxyl group-containing resins include polyethylene glycol, polybutylene glycol, polyalkylene glycol such as polypropylene glycol, and bisphenol A.
alkylene oxide adducts, polyester polyols (B) having various glycols and hydroxyl groups at the molecular chain ends, and the like. Among these, polyurethane acrylate resins obtained using polyester polyol (B) as one component are preferred.

The carboxylic acid component of the polyester polyol (B) includes terephthalic acid, isophthalic acid, orthophthalic acid, 1
, aromatic dicarboxylic acids such as 5-naphthalic acid, aromatic oxycarboxylic acids such as p-oxybenzoic acid, p-(hydroxyethoxy)benzoic acid, succinic acid, adipic acid, azelaic acid, cepacic acid, dodecanedicarboxylic acid, etc. unsaturated aliphatic and cycloaliphatic dicarboxylic acids such as fumaric acid, maleic acid, itaconic acid, tetrahydroheptalic acid, hexahydrophthalic acid, trimellitic acid, trimesic acid, pyromellitic acid, etc. and tetracarboxylic acids.

In addition, the glycol components of the polyester polyol (B) include ethylene glycol, propylene glycol, 1
, 3-propanediol, 1.4=phthanediol, 1
, 5-bentanediol, 1,6-hexanediol,
Neopentyl glycol, diethylene glycol, diethylene glycol, 2.2.4-trimethyl-1,3-
Bentanediol, 1,4-cyclohexane dimetatool, ethylene oxide and propylene oxide adducts of bisphenol A, ethylene oxide and propylene oxide adducts of hydrogenated bisphenol A, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, etc. be. Further, tri- and tetraols such as trimethylo-/I/x pn, trimethylolpropane, glycerin, and pentaerythritol may be used in combination. Other examples of polyester polyols include lactone-based polyester diols obtained by ring-opening polymerization of lactones such as ε-caprolactone.

The polyisocyanate (C) used in the present invention includes 2.4-tolylene diisocyanate, 2.6-tolylene diisocyanate, p-phenylene diisocyanate,
Biphenylmethane diisocyanate, m-7 22 diisocyanate, hexamethylene diisocyanate, tetramethylene diisocyanate, 3,3-dimethoxy 4,4-biphenylene diisocyanate, 2,4-naphthalene diisocyanate, 3,3'-dimethyl-4,4
'-biphenylene diisocyanate, 4.4-diphenylene diisocyanate), 4.4-diynecyane-)-diphenyl ether, 1.5-f7 tale diisocyanate, p-xylylene diisocyanate, m-xylylene diisocyanate, 1.3 - Diisocyanate compounds such as diisocyanatemethylcyclohexane, 1,4-diincyanatomethylcyclohexane, 4,4'-diincyanatodicyclohexane, 4,4'-diisocyanatecyclohexylmethane, inphorone diisocyanate, or 7 moles of all incyanate groups % or less of triisocyanate compounds such as a trimer of lylene diisocyanate and a trimer of hexamethylene diisocyanate.

Polyester acrylate resin is obtained by reacting a polyester polyol (B) containing a hydroxyl group or with the above-mentioned acrylic compounds (A-1) to (A-4) during the production of the polyester polyol (B). It is something.

The epoxy acrylate resin is obtained by reacting the acrylic compounds (A-1) to (A-5) with glycidyl group-containing epibis type epoxy resin or novolac type epoxy resin.

Various acid and rylate compounds include ethylene glycol,
These compounds can be obtained by reacting glycols such as neopentyl glycol, diethylene glycol, trimethylolpropane, and pentaerythritol with acrylic compounds (A-1) to (A-4).

One of the formative components of the radiation-curable resin of the present invention is a phosphorus compound represented by the above formula (1).

The structural formulas of representative examples of these phosphorus compounds are shown below.

Example of formula (1) Example of formula (2) O0 Example of formula [phase] ONa 0KO
Li ONa
0HOK OHONm OK 0Li
P(CH20H2CH20HzOH)2CIA)ONa ONa Na ONa ■ HOCH2CH20CH2-P-CH20CH2CH2
0HG? 7) Example of formula ω Oo I P(CH2CH2CH2CH20H)2 (to)
)OH ONa HOCIhCHzOCH2-P-CHzOCHzCHz
OH (46)?ゝ.

HOOCCHI CH2CH20CH2-P -CH2
0CH2CH2C0OH(48)OH HOCH2CH20CH2-P-CH20CH2CH2
0H(49)C2H6 HOCH2CH20CH2-P -CH20CH2CH
Example of formula (to) 20H(5o) The compound containing an aqueous polar group other than a phosphorus atom, which is one of the forming components of the radiation-curable resin of the present invention, represents an alkali metal, a tetraalkylammonium, or a tetraalkylphosphonium. , R1-R3 represent alkyl, aryl, or aralkyl having 1 to 8 hydrogen atoms. ) can be mentioned.

Specific compounds containing these hydrophilic polar groups are as follows.

(1) -COOM Polycarboxylic acid, glyceric acid, dimethylolpropionic acid, which is the acid component of the above polyester polyol (■),
Oxycarboxylic acids such as N,N-jetanolglycine and hydroxyethyloxybenzoic acid, aminocarboxylic acids such as diaminopropionic acid and diaminobenzoic acid, and derivatives thereof.

Nitrogen-containing alcohols such as N-methylgetanolamine, 2-methyl-I2-dimethylamine-methyl-1,3-propanol, 2-methyl-I2-dimethylamine-1,3-propanediol, and their picolinic acid, dipicolin Pyridine ring-containing compounds such as acids, aminopyridine, diaminopyridine, hydroxypyridine, dihydroxypyridine, aminohydroxypyridine, pyridine dimetatool, pyridinepropanediol, pyridineethanol, and derivatives thereof.

(4)-803M Polycarboxylic acids and derivatives such as 5-sodium sulfoisophthalic acid, 5-tetrabutylphosphonium, sulfoisophthalic acid, sodium sulfosuccinic acid, sodium sulfohydroquinone and alkylene oxide adducts, sodium sulfoisophthalic acid, sodium d' hozosphenol A and alkylene oxide adducts, etc.

These specific phosphorus compounds can be reacted through various processes. For example, polyester polyol (B),
It can be used as one component when producing raw material resins such as polyalkylene glycols and epoxy resins. In particular, when producing the polyester polyol (H), the phosphorus compounds represented by the above formulas (I) to (2) can be added and reacted at any stage before the completion of polymerization of the polyester polyol (B). From the operational point of view during production, it is preferable to add it after the transesterification reaction or after the esterification reaction.

Further, these specific phosphorus compounds can be used as one component of a raw material for radiation-curable resins such as polyurethane acrylate resins, polyester acrylate resins, epoxy acrylate resins, and acrylate compounds. For example, phosphorus compounds containing hydroxyl groups can be directly converted into isocyanate compounds (C) and polyester polyols (B).
By reacting with or acrylate compound (A),
Polyurethane acrylate resins can be produced.

Furthermore, among the specific phosphorus compounds of the present invention, diols are used as chain extenders for polyurethane acrylate resins, dicarboxylic acids are used as chain extenders for epoxy acrylate resins, and diols and dicarboxylic acids are used as chain extenders for polyester acrylate resins. good. Among these specific phosphorus compounds, mono(meth)acrylate of diol can be used as a chain extender for polyurethane acrylate resin, and monoethyloxy(meth)acrylate of dicarboxylic acid can be used as a terminal stopper for epoxy acrylate resin. good. Furthermore, poly(meth)acrylates of specific phosphorus compounds may be used as the acrylic compound.

The radiation-curable resin of the present invention is a raw material containing a raw material resin, etc., which is made by reacting an acrylic double bond-containing compound (A) with a specific phosphorus-based compound and a specific phosphorus-based compound by a known method. The molecular weight of the resulting resin is 500.
~1 (preferably 10,000).

It is appropriate to use the phosphorus compounds represented by the above general formulas (1) to (to) so that the phosphorus atoms are contained in the resin in an amount of 200 ppm to 50,000 ppm, and if the amount is smaller than the above range, the dispersibility for magnetic particles will be poor. On the other hand, if it exceeds the above range, there will be an increase in hygroscopicity, a decrease in physical properties, a decrease in adhesion to a non-att support, and the practicality will decrease.

Compounds containing a hydrophilic polar group other than these specific phosphorus compounds can be reacted as one component with the specific phosphorus compound in the same manner as when producing the raw material resin. It is particularly preferable to use it as a chain extender or terminal stopper. For polyurethane acrylate resin, diol etc. are used as a chain extender, or HOCH2CH2S is used as a terminal stopper.
O1Na, monoacrylate of glycol (1) listed in Table 2 below, etc. may also be used. For epoxy acrylate resins, dicarboxylic acid or the like may be used as a chain extender, or dicarboxyamine or the like may be used as a terminal stopper. As the polyester acrylate resin, chain extenders or terminal stoppers for the above-mentioned polyurethane acrylate resins and epoxy resins can be used. It is desirable that these hydrophilic polar groups exist in a range of 0.01 to 100 (equivalent ratio) to the phosphorus atom. More preferably, it is in the range of 0.1 to 1O.

If the hydrophilic polar group exceeds 100 (equivalent ratio) to the phosphorus atom, the adhesion to the base material will decrease, which is undesirable.
．． If it is less than 01, the stability of the magnetic coating material will be extremely impaired, which is not preferable.

In the present invention, in addition to resins reacted with phosphorus compounds represented by general formulas (1) to (2), we have developed a resin that can be used to adjust the flexibility of magnetic tapes, improve heat resistance, cold resistance, and abrasion resistance. For this purpose, it is desirable to add other compatible resins or to mix compounds that react with and crosslink with the resin of the present invention.

Examples of resins that are compatible with the resin of the present invention include vinyl chloride resins, polyester resins, cellulose resins, acrylic resins, epoxy resins, phenoxy resins, polyvinyl butyral, acrylonitrile-butadiene copolymers, and the like. Furthermore, examples of compounds that crosslink with the radiation-curable resin of the present invention include epoxy-based acrylic oligomers, spiran ring-containing acrylic oligomers, ether acrylic oligomers, acrylic threads, and acrylic oligomers with molecules of 31,200 to 10,000, such as polyhydric alcohols. .

As the ferromagnetic particles used in the present invention, bar-F
e203, r-F'e20B and Fe3O4 mixed crystal, CrO2, cobalt 7-elite, cobalt adsorbed iron oxide, barium ferrite, Fe-Co, Fe-Co-
Ferromagnetic alloy powder such as Ni can be used.

The magnetic recording medium of the present invention may optionally contain a plasticizer such as dibutyl 7-thalerate, triphenyl phosphate, dioctyl sulfonodium succinate-4, t-7'-thylphenol-polyethylene ether, ethylnaphthalene-4, etc.
Lubricating oils and various antistatic agents can also be added, such as sulfonic acid sorta, dilauryl succinate, zinc stearate, soybean oil lecithin, silicone oil.

Magnetic materials in which ferromagnetic powder is dispersed in a binder generally use a solvent, and examples of the solvent include ketones such as acetone, methyl ethyl ketone, methyl imbutyl ketone, and cyclohexanone, alcohols such as methanol, methyl acetate, Esters such as ethyl acetate, butyl acetate, and ethyl butyrate, glycol ethers such as ethylene glycol dimethyl ether, ethylene glycol monoethyl ether, and dioxane, aromatic hydrocarbons such as benzene, toluene, and xylene, and aliphatics such as hexane and heptane. Hydrocarbons or mixtures thereof can be used.

In the radiation-curable magnetic recording medium of the present invention, the magnetic material described above is coated on a non-magnetic support. Materials for the non-magnetic support that can be used include, for example, polyesters such as polyethylene terephthalate, polyolefins such as polypropylene,
Examples include cellulose derivatives such as cellulose triacetate and cellulose diacetate, polycarbonate, polyvinyl chloride, polyimide, metals such as aluminum and copper, and paper.

After a magnetic material is coated on a non-magnetic support according to a conventional method and dried, the coating film is calendered if necessary and then subjected to radiation treatment. Calendar treatment can also be performed after radiation treatment. In particular, as the radiation to be irradiated, in addition to electron beams, ionizing radiation such as neutron beams and gamma rays can be used.
The irradiation amount is preferably about 1 to 10 Mrad, especially about 2 to 10 Mrad.
8 Mrad is preferred.

(Function) By using it as at least one component of the binder, the resulting radiation-cured coating film can improve the dispersibility of magnetic particles while retaining its excellent mechanical properties. The properties, for example, the filling properties and orientation of the magnetic particles, and the smoothness of the magnetic layer are excellent, and the product has good durability with little powder falling off.

(Examples) Hereinafter, the present invention will be specifically explained using examples. In the examples, parts simply indicate parts by weight.

Example of producing polyester diol In an autoclave equipped with a thermometer and a stirrer, 485 parts of dimethyl terephthalate and 4 parts of dimethyl inphthalate were added.
85 parts of ethylene glycol, 409 parts of ethylene glycol, 485 parts of neopentyl glycol and tetrapoxy titanium) 0
．． 68 parts were charged and heated at 150 to 230°C for 120 minutes to perform transesterification.

Next, 50.1 parts of the phosphorus compound (13) was charged, and 2
The reaction was further carried out at 20-230°C for 1 hour. Next, the temperature of the reaction system was raised to 250°C in 30 minutes, the pressure of the system was gradually reduced to 10 mmHf after 45 minutes, and the pressure was further increased under these conditions for 6
The reaction continued for 0 minutes. Obtained polyester diol A
The molecular weight of is 2500. The phosphorus content was 1600 ppm.

Polyester diol B obtained by a similar manufacturing method
, E are shown in Table 1. The resin composition was analyzed by NMR. Polyester diol E in Table 81 showed no increase in viscosity during polymerization.

The structural unit of polyester diol E represents the molar ratio of the acid component and glycol component at the time of charging the raw materials.

Example of developing polyurethane acrylate resin In a reaction vessel equipped with a thermometer, a stirrer, and a reflux condenser, 72 parts of toluene, 72 parts of methyl ethyl ketone, and polyester diol A were placed.
After dissolving 100 parts, 21 parts of 4,4'-diphenylmethane diisocyanate and 0.0 parts of dibutyltin dilaurate.
After 5 parts of 2-methyl-
2 dimethylamino; 113-propanediol 7.1
of solids was added and reacted for further 5 hours until the solid content concentration was 40M1%.
A polyurethane acrylate resin solution was obtained. The solvent was evaporated from the reaction solution. Polyurethane acrylate resin A
The molecular weight of is 1 soo.

The phosphorus content was 1 l 100 pp.

By the same manufacturing method, polyester diols B to D,
From F, G to polyurethane acrylate resin B-c, I,
I got J. The obtained polyurethane acrylate resins are shown in Table 2.

Example 1 Comparative Example 1 Magnetic powder (cobalt coated γ-F'e20.) 6
0 parts Polyurethane acrylate resin A bath solution 30 parts (
Solid content concentration 50%, solvent methyl ethyl ketone/toluene = 1/1 fit ratio) 25 parts methyl ethyl ketone
Le en
25 parts methyl isobutyl ketone 2
After mixing 5 parts of the above composition in a ball mill for 24 hours, the magnetic paint was applied onto a 25 μm polyethylene terephthalate film to a dry thickness of 6 μm.

Next, magnetic field orientation treatment was performed in the length direction of the film using a DC magnetic field of 2500 Gauss for 0.05 seconds, and the temperature was 100°C.
, after drying with hot air for 1 minute, calendering was performed, and 5M
rad radiation treatment was performed.

A magnetizable layer was formed on a polyethylene terephthalate film in the same manner using a methyl ethyl ketone/toluene (1/1 heavy eyelid ratio) solution of the urethane-modified acrylate resin B shown in Table 2.

Table 3 shows the measurement results for each magnetic paint and magnetizable layer.

Table 3 (*): Magnetic paint was placed in a test tube to a height of 10 cIn, and after being left at room temperature for 24 hours, the height of the liquid level of the separated magnetic paint was measured.

(**): Visual judgment of the surface of the magnetizable layer.

(***) : Rub the paint film using methyl ethyl ketone-impregnated gauze.

(Number of rubbings required to expose the base material) Production side of epoxy acrylate resin In a reaction vessel equipped with a thermometer, a stirrer, and a reflux condenser, 150 parts of toluene and Epicoat 828 (Shell Petrochemical Industries ■IJ) were placed. After dissolving 100 parts of the phosphorus compound (12
), and heated at 80 to 100°C for 160 minutes to react.Next, 54 parts of acrylic acid and 0.01 part of hydroquinone as a stabilizer were charged, and reacted at 80 to 100°C for 180 minutes. The molecule f of the obtained epoxy acrylate (A) is 700, and the phosphorus content is 1tIIi 2600.
ppm, oxidation was 0.8 KU) I (~h).

Example 2 A magnetizable layer was formed on a polyethylene terephthalate film in the same manner as in Example 1 except that epoxy acrylate resin A was used instead of the polyurethane acrylate resin A solution in Example 1.

Table 4 shows the measurement results for each magnetic paint and magnetizable layer.

Table 4 ((E): A 500μ aluminum sheet is used as the base material.

(Effects of the Invention) In the present invention, the radiation-curable resin containing a phosphorus compound and another hydrophilic polar group-containing compound is more effective for magnetic coatings than those containing either one of them (polyurethane acrylate resin door and J). Excellent stability, squareness ratio (Br/8m), and smoothness.

Claims (1)

[Claims] A radiation-curable magnetic recording medium in which a magnetic material in which ferromagnetic powder is dispersed in a binder is coated on a non-magnetic support and cured by radiation, wherein at least one acrylic double bond is present in the molecule.
A radiation-curable resin that is made by reacting at least one phosphorus compound represented by the following formulas (I) and (V) with a hydrophilic polar group-containing compound other than a phosphorus atom is used as a component of the above-mentioned binder. A radiation-curable magnetic recording medium characterized by: ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (I) ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (II) ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (III) ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ ( IV) ▲Mathematical formulas, chemical formulas, tables, etc.▼(V) [X, Y are ester-forming functional groups, R_1 has 3 to 3 carbon atoms
10 trivalent hydrocarbon groups, R_2 is an alkyl group having 1 to 12 carbon atoms, a cycloalkyl group, an aryl group, and 1 to 12 carbon atoms.
12 shows an alkoxy group, a cycloalkoxy group, or an aryloxy group. Aryl and aryloxy groups are halogen atoms, hydroxyl groups, -OM'(M' represents an alkali metal)
Alternatively, it may be one with an amino group bonded to it. R_3, R_
4 is an alkylene group having 1 to 12 carbon atoms, a cycloalkylene group, an arylene group, the following formula: -(CH_2-OR_5)
A group represented by -_m (R_5 represents an alkylene group having 1 to 12 carbon atoms, a cycloalkylene group, or an arylene group. m
can take any value from 1 to 4. ), M represents an alkali metal atom, hydrogen, a monovalent hydrocarbon group, or an amino group. ]