JPS6038721A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a recording medium having superior surface smoothness, electromagnetic characteristics and mechanical strength by forming an undercoat layer contg. an ultraviolet-curing oligomer or polymer having unsatd. double bonds and a surfactant between a transparent plastic film support and a magnetic layer. CONSTITUTION:An undercoat layer contg. 100pts.wt. in total of one or more kinds of oligomers and/or polymers each curable with radiation such as ultraviolet rays or electron beams and having one or more unsatd. double bonds in one molecule and 0.3-30pts.wt. anionic, nonionic or amphoteric surfactant as an antistatic agent is formed on a transparent plastic film support. A magnetic layer contg. magnetic powder dispersed in a binder resin is then formed on the undercoat layer. Though neither the front side of the magnetic layer nor the back side is subjected to antistatic treatment, the magnetic layer has low surface resistance, and a magnetic recording medium solving problems such as sticking, ununiform winding and drop-out is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a magnetic recording medium that has excellent antistatic properties and surface smoothness, and has good electrical properties.

Currently, many magnetic recording media such as audio tapes, video tapes, and magnetic disks are made by using magnetizable metal powder such as iron oxide on plastic films such as polyester or polyvinyl chloride, or base films such as paper. It is created by applying a paint containing it, orientation, drying calendering, and if necessary curing.

Various thermoplastic resins or thermosetting resins are used as the material for this paint, but the pigment concentration in the paint is high and it does not adhere well to the surface of the base film. For example, the magnetic layer may fall off when a strong instantaneous stress is applied to the tape.

In order to increase this adhesive strength, a nonmagnetic undercoat layer (one layer of primer) is provided on the base film. Various thermoplastic resins or thermosetting resins are used as the resin binder used for forming the primer layer. When a thermoplastic resin primer is used, when applying a magnetic paint containing a large amount of solvent, the already formed primer layer swells or dissolves due to the solvent, causing uneven coating and loss of smoothness of the magnetic layer. There's a problem. When a thermosetting resin primer is used, the above-mentioned problems can be avoided, but there is an industrial disadvantage that a magnetic layer cannot be continuously formed because a long heat curing treatment is required.

The above-mentioned problem in primer processing of magnetic recording media can be solved by using a prescribed radiation-curable resin as a binder for forming the primer, which forms a single layer of primer with extremely good solvent resistance and adhesive properties in a short time.
By continuously applying a magnetic layer, a magnetic recording medium with excellent surface smoothness, electrical properties, and mechanical strength can be obtained.

That is, a non-magnetic undercoat layer (primer F7t) is applied to the support.
In a magnetic recording medium in which a magnetic layer is formed after applying , the undercoat layer has, for example, two or more (meth)acryloyl groups in one molecule, and the molecular weight per (meth)aryloyl group is A magnetic recording medium formed by radiation irradiation using a radiation-curable paint such as a paint containing one or more oligomers or polymers having a molecular weight of 200 or more, and optionally a solvent or a photopolymerization initiator. The above effects are achieved.

Such a primer single-layer paint is applied to a base material and then irradiated with radiation to form a coating film with a three-dimensional network structure through radical polymerization, and when the magnetic layer is applied, The smoothness of the magnetic layer can be maintained without causing swelling due to solvent.

The magnetic recording medium obtained in this way has excellent surface smoothness,
Adhesion is also good, but frictional electrification occurs when the tape is run, and so-called peel-off electrification occurs when the magnetic surface separates from the base surface when the tape-wrapped body is run, which causes dirt, dust, etc. Minute shavings from the base or magnetic surface adhere to the magnetic surface and cause dropouts. Recently, some base films have a thickness of about 11 μm or less, and while an extremely thin high-performance magnetic layer is formed on the surface, the spacing between the magnetic head and the tape magnetic surface is kept as small as possible. It has become necessary to record up to high frequencies, and even if the dirt and dust is minute, it greatly affects the spacing and causes dropouts.

In addition, if such charging occurs, the uniformity of the running of the magnetic recording medium is disturbed, especially during the manufacture of the magnetic recording medium, the winding appearance of the tape becomes poor, and the control of the manufacturing process becomes regressive. Moreover, the winding appearance of the product tape also deteriorates.

As a countermeasure to these problems, a back layer is formed on the base surface opposite to the magnetic surface, and if an inorganic conductive powder such as carbon black is dispersed in the back layer, a magnetic recording medium having a predetermined conductivity can be obtained. I can do it. However, no;
Although the thick layer is formed on Primer J as a separate layer in addition to 1, it requires an extra step.

An object of the present invention is to provide a magnetic recording medium that does not use the above-mentioned back layer, has low chargeability, and has little dropout.

Briefly stated, the present invention involves dispersing an antistatic surfactant in a radiation-curable coating containing molecules with a curable double bond, and applying this to Primer BJ.
By using it as a magnetic recording medium, it has similar charging properties, excellent surface smoothness, and good paper adhesion. '＋
i'f Carbon black may be used in combination as an anti-static polisher, but if too much is used, the surface of the primer W becomes rough and the surface smoothness of the magnetic layer is impaired. According to this book, even though neither the magnetic surface nor the back surface is antistatically treated, the surface resistance of the magnetic surface is reduced to 1111, causing irregular winding and dropouts due to charging and tape sticking. can solve the problem.

The resin components of the radiation-curable paint used in the present invention are:
Contains at least two radiation-crosslinkable double bonds in one molecule, including acrylic double bonds, allyl yarn double bonds, maleic double bonds, and other radiation-crosslinkable double bonds. Included are oligomers or polymers containing linkages.

Preferably, the molecule has two or more (meth)acrylic groups, and the molecular weight per (meth)acrylic group is 20.
Compounds that are 0 or more may be used. If the number of molecular needles per (meth)acrylate group is 200 or less, a large volumetric shrinkage occurs during the crosslinking and curing reaction, and the base material curls.
It is known that dimensional stability is poor and adhesion is significantly reduced.

Many low-molecular-weight compounds have low boiling points, which may evaporate and scatter during drying and curing, causing industrial problems.

However, even such low molecular weight monomers can exhibit excellent properties when used in combination with higher molecular weight monomers.

Radiation a! Especially when using a mixture of two or more curable oligomers or polymers, (4) a compound having a molecular weight of 5,000 or more, preferably 8,000 or more and having two or more unsaturated double bonds that are curable by radiation; ( B) 1 unsaturated double bond that is curable by radiation
having a molecular weight of 400 or more and less than 5000,
Preferably a compound having a molecular weight of 600 to 3,000, (C) a compound having a molecular weight of less than 400 and having one or more unsaturated double bonds that are curable by radiation, and at least two selected from the above (4) and (B8 (C)). Excellent effects can be obtained by using a radiation-curable paint containing the above.Furthermore,
The radiation-curable paint contains at least two or more selected from (B) and (C), and (5) is D to 90% by weight, (B) is 0 to 80% by weight, and (C) is 0-50%
It is best to use it at a mixing ratio of It is also possible that the radiation-curable paint contains (4) and (B) in a blending ratio of 20 to 95% by weight of (6) and 5 to 80% by weight of part. Furthermore, the radiation-curable paint may contain 1 to 10% by weight of a photopolymerizable sensitizer.

Examples of these compounds are:

1 per molecule of a compound having one or more hydroxyl groups in the molecule
One isocyanate group of a polyisocyanate compound of more than one molecule is reacted, and then a reaction product with one or more molecules of a monomer having a group that reacts with the isocyanate group and a radiation-curable unsaturated double bond, such as propylene. 1 mol of bifunctional polyether (ADEKABORIETEL P-1000 Asahi? Ukasha M), which is a difunctional polyether prepared by adding propylene oxide to glycol, is reacted with 2 mol of toluene fucyanate, and then 2 mol of 2-human tetraxyethyl methacrylate is reacted. Examples include resins, prepolymers, oligomers, and telomers having two acrylic double bonds at the molecular ends obtained by reacting the above.

Compounds containing one or more hydroxyl groups used here include ADEKA Polyether P-700゜ADEKA Polyether P-1000, ADEKA Polyether G-1500 (
(manufactured by Asahi Denka Co., Ltd.), Polymeg 1000, Polymeg 65o
(Forker-Cola Company I!!) and other polyfunctional polyethers; cellulose derivatives such as Nidogastricel P-s, acetyl-7-Rose, and ethyl cellulose; and vinylite V.
Partially saponified vinyl chloride-vinyl acetate copolymer with hydroxyl groups such as AGH (manufactured by Union Carbide, USA) Polyvinyl alcohol gourd Polyvinyl formal-rich polyvinyl butyral 1 Polycarb tetralactine PCP-02
Polyfunctional polyesters such as 00, polycaprolactone PCP-0240, polycaprolactone PCP-0300 (manufactured by Chisso Corporation), mt saturated polybases such as phthalic acid, isophthalic acid, terephthalic acid, adipic acid, succinic acid, and sepacic acid. Acid and ethylene glycol, diethylene glycol, 14-butanediol, t3-butanediol,
t2-propylene glycol: a saturated polyester obtained by ester bonding with polyhydric alcohols such as t2-propylene glycol, diethylene glycol, 16-benzene glycol, neopentyl glycol, glycerin, trimethylalcohol, pentaerythritol, etc. Examples include acrylic polymers containing at least one kind of acrylic ester and methacrylic ester containing hydroxyl groups as polymerization components.

In addition, the polyisocyanate compounds used here include 2.4-) luene diisocyanate, 2.6-)
(ruene diisocyanate), t4-xylene diisocyanate, m-phenylene diisocyanate), p-phenylene diisocyanate, hexamethylene diisocyanate, inphorone diisocyanate and desmodur L1
Examples include Desmodule IL (manufactured by Bayer AG, West Germany).

Examples of monomers having a group that reacts with an incyanate group and a radiation-curable unsaturated double bond include 2-hydroxyethyl ester of acrylic acid or methacrylic acid, 2-hydroxyethyl ester of acrylic acid or methacrylic acid;
Acrylic alcohol, maleic acid polyhydric alcohol ester compounds, which have active hydrogen that reacts with isocyanate groups such as hydroxypropyl ester, 2- to hydroxyoctyl ester, etc. Acrylic alcohol, maleic acid polyhydric alcohol ester compound, Also included are monomers containing unsaturated double bonds that have active hydrogen that reacts with mono- or di-glysocyanate groups of long-chain fatty acids that have unsaturated double bonds, and that are radiation-curable.

■ A reaction product of one molecule of a compound containing one or more epoxy groups in the molecule and one or more molecules of a simple compound having a group that reacts with the epoxy group and an electron beam curable unsaturated double bond, such as glycidyl methacrylate, is used as a radical. Resin, prepolymer or oligomer made by reacting thermoplastic fid resin containing epoxy groups obtained by polymerization with acrylic acid, and pentanting acrylic double bonds in the molecule through a vote-cutting reaction between carboxyl groups and epoxy groups. Further, examples thereof include resins, prepolymers, and oligomers having radiation-curable unsaturated double bonds in their molecular skeletons by reaction with maleic acid and ring-opening reaction between carboxyl groups and epoxy groups.

Examples of compounds containing one or more epoxy groups in the molecule include Yume Epicote 828, a homopolymer of acrylic ester or methacrylic ester containing epoxy groups, such as glycidyl acrylate and glycidyl methacrylate, or a copolymer with other polymerizable monomers; Epicote 1
There are various other types of epoxy resins such as 001, Ebicor) 1007, and Epifut 1009 (all manufactured by Shell Chemical Company!!!).

Examples of monomers having groups that react with epoxy groups and radiation-curable unsaturated double bonds include sulfur acrylic thread monomers containing carboxyl groups such as methacrylic acid, methylaminoethyl acrylate, and methylaminomethacrylate. In addition to acrylic monomers having primary or secondary amino groups, single polybasic acids having radiation-curable unsaturated double bonds such as maleic acid, fumaric acid, crotonic acid, and undecylenic acid can also be used.

l A reaction product of one molecule of a compound containing one or more carboxyl groups in the molecule and one or more molecules of a monomer having a group that reacts with carboxyl groups and a radiation-curable unsaturated double bond, such as methacrylic acid, is dissolved in a solution. A resin in which an acrylic double bond is introduced into the molecule by reacting glycidyl methacrylate with the thermoplastic resin containing a carboxyl group obtained by the above process, and by a ring-opening reaction between the carboxyl group and the epoxy group as in item 1. , prepolymers, and oligomers.

Examples of compounds containing one or more carboxyl groups in the molecule include polyesters containing carboxyl groups in the molecular chain or at the end of the molecule; compounds with radical polymerizability such as acrylic acid, methacrylic acid, maleic anhydride, and fumaric acid, These include homopolymers of monomers having groups or copolymers with other polymerizable monomers.

Glycidyl acrylate is a monomer having a group that reacts with a carboxyl group and a radiation-curable unsaturated double bond.
(, glycidyl methacrylate, etc.).

■ A polyester compound containing a radiation-curable unsaturated double bond in its molecular chain, for example, a saturated polyester resin consisting of an ester bond of a polybasic acid and a polyhydric alcohol as described in item 1, in which a part of the polybasic acid is Maleic L1/unsaturated polyester resins, prepolymers, and oligomers containing closed radiation-curable unsaturated double bonds can be produced.

Examples of the polybasic acid and polyhydric alcohol components of the saturated polyester resin include the compounds listed in Section 1.
Examples of radiation-curable unsaturated double bonds include maleic acid and fumaric acid.

The radiation-curable resin-based polyester resin is produced by adding maleic acid, fumaric acid, etc. to one or more polybasic acid components and one or more polyhydric alcohol components, using a conventional method, that is, in the presence of a catalyst.
After dehydration or dealcoholization in a nitrogen atmosphere at ~200℃, the temperature is raised to 240~280℃, and the temperature is increased to 0.5~lmmH.
A polyester resin can be obtained by the combined reaction of g under reduced pressure. The content of maleic acid and fumar W% is the acid component % based on crosslinking, radiation curing, etc. during production.

■ Low-molecular-weight compounds that bind radiation-curable unsaturated double bonds can also be used depending on the purpose; such low-molecular-weight compounds include styrene, ethyl acrylate,
Ethylene glycol diacrylate, ethylene glycol dimethacrylate, diethylene glycol diacrylate, diethylene glycol dimethacrylate, 1.6
-hexane gelicol diacrylate), i,6-hexane gelicol dimethacrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, etc. be).

The radiation-curable paint in the present invention can be obtained by using the compounds described in Items 1 to 7, but it is also possible to use a compound containing an acrylic double bond with a molecular ff of 14.00 or more alone. However, in that case, as the molecular weight increases, the electron beam curability tends to decrease due to the functional group density, thus requiring a high line pattern, and as the curability decreases, the heat resistance also tends to deteriorate. In addition, the adhesiveness may decrease as the curability increases.

On the other hand, in the case of an electron beam curable resin having a molecular weight of less than 400, the electron beam curability is good and the solvent resistance, heat resistance, etc. are good, but there is a problem in adhesiveness. In this way, when a compound compound containing an acrylic double bond and having a molecular weight of 400 or more or less than 400 is used alone, it is possible to obtain an undercoat paint that satisfies a wide variety of properties required for magnetic recording media in a well-balanced manner. It's recorded.

On the other hand, when two or more types of compounds having different molecular weights are blended, good adhesion and curability can be obtained.

In the present invention, if necessary, a non-reactive solvent is used. Although there is no particular restriction on the solvent, it is appropriately selected in consideration of the solubility and compatibility of the binder. For example, acetone
Ketones such as methyl ethyltetone, methyl inteton, cyclohexanone, esters such as ethyl formate, ethyl acetate, butyl acetate, alcohols such as methanol, ethanol, isopropanol, butyl, toluene, xylene , aromatic hydrocarbons such as ethylbenzene MG
U, ethers such as isopropyl ether, ethyl ether, and dioxane, and hexaranyl compounds such as tetrahydrofuran and furfural are used as a single solvent or as a mixed solvent. Of course, it can be formed using a curable resin as a vehicle, or it can be formed by radiation irradiation using a radiation curable resin such as that used for the primer layer. You can also do it.

The substrate on which the single layer of primer and the magnetic paint according to the present invention are applied include polyethylene terephthalate film, which is currently widely used as a substrate for magnetic recording media;
Further, for applications requiring heat resistance, polyimide films, polyamide films, etc. are used. In particular, for polyester films, uniaxial stretching and 2
In many cases, it is used after being subjected to axial stretching treatment. It is also used to coat paper.

The radiation used for crosslinking and curing the radiation-curable paint according to the present invention is an electron beam Co using an electron beam accelerator as a radiation source.
γ-rays are used as a source, β-i sources are Sr, and X-rays and ultraviolet rays are used as sources. In particular, as an irradiation source, it is advantageous to use electron beams or ultraviolet rays from an electron beam accelerator from the viewpoints of controlling the absorbed dose, introducing into the manufacturing process line, blocking ionizing radiation, etc.

The characteristics of the electron beam used when curing magnetic coatings are as follows:
From the viewpoint of penetrating power, it is convenient to use an electron beam accelerator with an accelerating voltage of 100 to 750 KV, preferably 150 to 500 KV, and to irradiate at an absorbed dose of α5 to 20 Megaland.

The radiation-curable coating material of the present invention can also be cured by ultraviolet rays by adding a photopolymerizable Jn sensitizer.

The photopolymerization sensitizer may be a conventionally known one, such as benzoin series such as hahenzoin methyl ether, benzoin ethyl ether, α-methylbenzoin α-chlordeoxybenzoin, benzophenone, ace)phenone bisdialkylaminobenzophenone, etc. Examples of photopolymerization sensitizers include quinones such as enanthraquinone, anthraquinone, and 7-enanthraquinone; sulfides such as benzyl disulfide and trimethylthiuram monosulfide; On the other hand, a range of 0.1 to 10% is desirable.

Hereinafter, the present invention will be specifically explained with reference to Examples and Comparative Examples. In addition, "part" and "%" in the examples indicate the heavy plate part and the nail needle percentage.

Prior to the examples, we will show examples of resin synthesis.
After heating and dissolving 100 parts of a 2/5 copolymer with a molecular weight of 18,000 in a composition of 1% by weight and 238 parts of toluene and 95 parts of cyclohexanone, the temperature was raised to 80°C, 15 parts of the following TDI adduct were added, and further 0.5 parts of tin octylate was added. 002 parts and 1002 parts of hydroquinone were added in an Nt gas stream at 82"'C, and the anti-IJis rate was 90%.
Let it react until it reaches the above level. After the reaction is completed, the mixture is cooled and diluted with 238 parts of methyl ethyl ketone. The obtained resin star composition is referred to as (a). The molecular weight of this resin is 192
00, and the molecular weight per methacryloyl group is about 4,400.

Synthesis of TDI adduct 348 parts of tolylene diisocyanate (TDI) was mixed with N,
After heating to 80°C in a 4-hole flask in an air stream, 2-hydroxyethyl methacrylate (2JIEMA) 26
Part, tin octylate O, 07 fjls, and 0.05 part of noidoquinone were added dropwise while controlling the cooling so that the temperature of the warm ash in the reaction vessel was 80 to 85°C, and after the sieving was completed, it was heated at 80°C for 3 hours. Stir to complete reaction 6. After completion of the reaction, take out and cool, white paste TDI 2HEM
I got an A adduct.

Resin synthesis example (b) fl polynisder resin (L- manufactured by Dynamide Nobel)
411) 100 parts of toluene and 116 parts of methyl ethyl ketone were heated and dissolved, and the temperature was raised to 80°C, followed by synthesis of isophorone diisocyanate)-
Add 2.84 parts of tin octylate (amino), further add 0.006 parts of tin octylate, and 0.006 parts of hydrogynone, and react at 80°C in a N gas stream until the NGO reaction rate is 90% or more.O Obtained resin composition Let the object be (c). Molecule f of this resin
2 is 20600.

(Seedling fat synthesis example (C) 2912 parts of dimethyl terephthalate, 291.2 parts of dimethyl isophthalate, 64.8 parts of dimethyl maleate, 25 tons of ethylene glycol, 3 parts of 1,4-butanediol
64.8 parts of 1,6-butanediol, 812 parts of 1,6-butanediol, and 4.0 parts of tetra-n-butyl titanate) were charged into a reaction vessel. After demethanol reaction at 180 °C in a gas stream, 24
A linear unsaturated polyester resin having a molecular weight of 8,000 was obtained by a synthesis reaction at a temperature of 0 to 260°C and a reduced pressure of 0.5 to 1 mmHg.

Resin Synthesis Example (d) 250 parts of NIAX Poly, t-ru PcP-0200 (FSO Co., Ltd. Polycarb Pcicton), 122.2 parts of 2-hydroxyethyl methacrylate, 0.024 parts of hydroquinone
and 33 parts of tin octylate α0 were placed in a reaction vessel and heated to 80°C.
After heating and dissolving 1616 parts of TD, the temperature inside the reaction vessel was 8.
It is added dropwise while cooling to a temperature of 0 to 90'C, and after the completion of the dropwise addition, it is allowed to react at 80°C until the NGO reaction rate reaches 95% or more. The resulting fat composition is referred to as (d).

The molecular weight of this resin is 1140. The molecular weight per methacryloyl group of this resin is about 600.

Resin synthesis example <6) 148 parts of 7-talic anhydride, 65 parts of t3-butanediol,
30 parts of ethylene glycol and 2.5 parts of para-toluene sulfone were placed in a reaction vessel, and after esterification reaction for 1 hour, the mixture was cooled to 100°C, and 3 parts of hydrochloric acid α and 28 parts of acrylic acid were added, and the esterification reaction was continued for 15 hours. An oligoester acrylate having a molecular weight of 2000 was obtained. The molecular weight per acryloyl group of this resin is about 650.

Resin synthesis example <f) 250 parts of ADEKA Polyether P-1000 (Asahi Denka t-polyether), 2-human 1:1-? 65 parts of diethyl methacrylate), 15 parts of Hyde aq non α0, and 017 parts of tin octylate were placed in a reaction vessel, and after heating and dissolving at 80°C,
87.0 parts of TDI was added at a temperature of 80 to 90 in the reaction vessel.
Dropped while cooling to 80℃ after dropping.
The reaction is allowed to proceed until the NGO reaction rate reaches 95% or more. The obtained resin composition is defined as (f>. The molecular weight of this tree Pk+ is 1610, and the molecular weight per methacryloyl group is about 800.

The surfactant as an antistatic agent used in the present invention is
Examples of the anionic type include carboxylate, sulfuric acid conductor, phosphoric acid Firt 8, pentaargyl polyphosphate, hexaalkyltetrapolyphosphate, dialkylphosphophone, sulfone rJν, and the like.

Further, as cationic types, there are amines, quaternary ammonium salts, imidacillin, amine oxidized ethylene adducts, and phytic acid quaternary hemorrhoids.

Nonionic types include polyhydric alcohols, polyalcohol esters, alkyl faire/fluorinated ethylene,
Fatty acid ethylene adduct, amide oxidized ethylene adduct,
These include amine oxidized ethylene adducts, amides, etc.

Examples of amphoteric types include carboxylic acids, sulfonic acids, gold-14 salts, and alkyl betaines.

If the amount of surfactant is less than 1 part by weight based on the resin, it will not have the antistatic effect of the Tsuku layer, and if it is more than 20 parts by weight, it will bleed onto the surface and will not last long. .

Further, as these surfactants, an acrylic material may be used at the end.

In addition to the surfactant, pigments such as SiO, Ti01, AL, and O
,,Crto8. S iC, CeO,, CaCo3,
Zinc oxide, goethite, αFe@O1, talc, kaolin, case, boron nitride, Teflon powder, graphite fluoride, molybdenum disulfide, zirconia, Ca5iOt, asbestos, titanium white, white carbon, chrome yellow, oil yellow, oil Blue, oiled pue, etc. are added as appropriate.

In addition, is the surfactant and R1 material necessarily 1f? It is not always necessary to use one by one; two or three types may be mixed.

The surfactant is 0.00% based on the curing component of the primer layer.
It can be used in amounts of 3 to 30% by weight.

In addition, when carbon black is used in part, it is 10 to 3
00μ average particle size and 1% of the curing component of the primer.
It can be contained in a ratio of 0.3 to 30 parts. When the carbon black is in this range, the surface properties of the magnetic layer are not substantially impaired, and on the other hand, the tendency to stick to guide rollers and the like used during the manufacturing process is reduced, which is preferable.

According to the present invention, the surface resistance of the magnetic layer ranges from about 1011Ω/F2 to 108 to 10@Ω when the primer does not contain surfactant or surfactant and carbon black.
It was found that the dropout was reduced to about /-2, and the winding appearance of the tape especially during the manufacturing process was improved. In the following, "parts" are based on weight.

Example 1 A radiation-curable paint was prepared by mixing 40 parts of the resin composition (a) with a solvent (toluene/meth). This paint was applied onto a polyester film to a dry film thickness of 0.1 μm.
After drying, electron beam irradiation was performed in an N2 atmosphere at an irradiation dose of 2 Mrad using an electrocurtain electron beam irradiation device manufactured by ESI Co., Ltd. to provide a single layer of crosslinked and hardened primer.

Next, the following magnetic paint was applied thereon to a dry thickness of 2.5 μm, and after drying, the film was subjected to a surface smoothing treatment and cut into pieces of 2 inch pieces to obtain video tapes.

Manufacturing method of magnetic paint Nitrocellulose (manufactured by Asahi Kasei ■ 11/2") 8 parts V
To the resin solution obtained from AGH (manufactured by Union Carmade) 10 parts methyl isobutyl ketone 150 parts cyclohexanone 50 parts, Fe-N1-(:o alloy powder 100 parts α-AI, 03
((L5μ5μ) 2 parts repellent (higher fatty acid modified silicone oil) 1 part dispersant (soybean oil refined lecithin) 3 parts were blended and dispersed in a ball mill for 24 hours to prepare a magnetic paint.

Example 2 Surfactant (tertiary amine) 1 part the above resin composition (Li) 7 parts NK ester-A-4G (Shinchuban Kagaku) 3 parts H agent (
) Luene/methyl ethyl ketone = 1/1) 90 parts The mixture of the above compositions was thoroughly mixed and dissolved to prepare a radiation-curable undercoating paint. This paint was applied onto a polyester film to a dry film thickness of 02 μm,
After drying, electron beam irradiation was performed under N atmosphere with an irradiation IJI amount of 5M land to provide a single layer of crosslinked and cured primer.

Next, a magnetic layer was provided in the same manner as in Example 1 to produce a videotape.

Example 3 Surfactant (alkyl betaine type) 0.5 parts Said resin composition (b) 6 parts Said resin composition (e) 3 parts 1.6 Hegisan glycol diacrylate 1 part I
D-luene/methyl ethyl ketone = 171) 90 parts The mixture of the above compositions was thoroughly mixed and dissolved to prepare a radiation-curable undercoating paint. This paint is applied onto a polyester film to a dry film thickness of 0.1μ,
After drying, N,
A single layer of crosslinked and cured primer was provided by electron beam irradiation in an atmosphere.

Next, the following magnetic layer was formed.

(Radiation-curable paint layer) Dispersant (oleic acid) 2 parts Solvent (methyl ethyl ketone/toluene = so/5o) 1
00 parts The above composition was mixed for 3 hours with a high-power mixer, and then 10 parts of acrylic double bond-introduced polyester urethane oligomer, 5 parts of Vinyrite VAGH, 10 parts of acrylic double bond-introduced polyether urethane oligomer, solvent (methyl ethyl ketone/toluene-50150) 2
A magnetic paint was prepared in the same manner as in Example 1 using 3 parts of higher fatty acid (myristic acid), and this magnetic Gl
After coating the material on the same machine and smoothing the surface, apply an acceleration voltage of 150
The coating film was cured by irradiation with an electron beam in an N2 atmosphere under conditions ζ of a key current of 10 TILA and an absorption amount of 5 Mrad.

Example 4 0.2 parts of carbon black (20 mμ) 40 parts of the resin composition (a) 4 parts of the resin composition b) 4 parts Solvent (toluene/methyl ethyl ketone = 1/1) 56
A radiation-curable undercoating paint was prepared by thoroughly mixing and dissolving the mixture of the above compositions. After drying this paint on a polyester film, ESI
Using an electrocurtain type electron beam accelerator manufactured by
An electron beam was irradiated in an Nt atmosphere under the conditions of an acceleration voltage of 160 KV, an electrode current of 10 mA, and an irradiation dose of 3 Mland to cure the coating film and provide a primer layer. A magnetic layer was formed in the same manner as in Example 1.

Comparative example 1 Solvent (toluene/methyl ethyl ketone = 1/1) 9
A magnetic layer was formed in the same manner as in Example 1, except that a paint obtained by mixing and dissolving the above composition was applied to a polyester film to a dry thickness of 0.1μ, dried, and an undercoat layer was formed. A videotape was made.

Comparative Example 2 The resin a, [acid (a) 50 parts solvent (toluene/methyl ethyl ketone = 1/1) 50
The above composition is mixed and dissolved, and the radiation curable paint is vta
vv L/, a videotape was produced in the same manner as in Example 1.

Comparative Example 3 Example 1 without an undercoat layer. Examples 1-4
, for the samples of Comparative Examples 1 to 6, the peel strength of the coating film and the video sensitivity on the VHS deck (RF4MH2)
The results of the measurements are shown in Table 1. Regarding adhesion, it can be seen that all the samples on which the primer layer was formed provided magnetic tapes with better winding shape than Comparative Examples 1 and 2, which did not contain a surfactant.

In addition, the surface resistance of the magnetic surface was reduced in all samples, and it can be seen from the dollar-out value that the magnetic surface of the present invention is superior.

As described above, in the present invention, the portion exposed on the surface has "41".
Reducing static charge and other effects can be achieved by imparting conductivity to only one layer of the primer without applying electrical treatment.
No need to complete the process of forming a back layer or surface layer.

Moreover, during the manufacturing process, dirt and dust become magnetic while passing through various guide rollers. Above all, the magnetic recording device of the present invention is excellent in this aspect as well.

Example 1.2.30 The adhesion during running is in the inaudible range, but the adhesion during running can be further suppressed by adding a pigment, for example, carbon.

□□□□□□□□□ Same Kurahashi ゛　□゛） Continuation of page 1 0 shots Mingsha Island 1) Shigeru Shigeru Company, Chuo-ku, Tokyo 0 shots Akira Kubo 1) Yu - Inside Shikisha, Chuo-ku, Tokyo

Claims (2)

[Claims] (1) A magnetic recording medium consisting of a transparent plastic film support, an undercoat layer formed on the surface thereof, and a magnetic recording layer formed on the surface of the undercoat layer, in which the undercoat layer is a non-hardened material that is cured by radiation. A magnetic recording medium characterized in that it is made by adding a surfactant to one or more oligomers or polymers containing one or more saturated double bonds per molecule and curing the mixture with radiation. (2) The magnetic recording medium according to claim 1, wherein the surfactant is used in an amount of 0.3 to 30 parts by weight per 100 parts of the oligomer or polymer.