JPS60187926A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain an excellent magnetic recording medium without using a radiation irradiating device by dispersing fine ferromagnetic particles into a binder contg. a specific radiation-sensitive soft resin or the prepolymer, etc. thereof, adding a polyhydric isocyanate compd. thereto and curing the mixture composed thereof by crosslinking. CONSTITUTION:A soft resin formed by introducing radiation sensitive unsatd. bonds such as acrylic double bonds, maleic double bonds, allyl double bonds, etc. into a vinyl chloride/vinyl acetate/vinyl alcohol copolymer, satd. polyester resin, etc. or the mixture of the prepolymer, oligomer or telomer thereof and either of a thermoplastic resin having no radiation-sensitive double bonds or the modified resin which has the above-described radiation sensitive double bonds and is not soft is mixed as a binder with ferromagnetic powder and thereafter polyhydric isocyanate is added to prepare a magnetic coating. Such coating is coated on a substrate surface and is then cured by heating without using radiation irradiation. The magnetic recording medium having excellent runnability, electromagnetic conversion characteristic, durability, etc. is thus obtd.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a magnetic recording medium, and more particularly, the present invention relates to a magnetic recording medium, and more specifically, a radiation-sensitive resin is used as a binder, and a crosslinking agent typified by a polyvalent isocyanate group-containing compound is added to the binder. Add,
This invention relates to a magnetic recording medium that has a three-dimensional network structure.

<Prior art> Conventionally, thermosetting resins containing polyvalent isocyanate groups have been used as binders to prevent the magnetic coating film of magnetic recording media from falling off and to improve the durability, running characteristics, and environmental reliability of magnetic recording media. A strong crosslinking bond is obtained by heating a compound to which it has been added.

Furthermore, a radiation-sensitive resin is used as a binder, and the resin is irradiated with radiation to cause crosslinking and polymerization.

<Objective of the Invention> The object of the present invention is to reduce the dimensional stability caused by thermal deformation of the base material of a magnetic recording medium such as a polyester film, which occurs when a thermosetting resin is used, by using a radiation-sensitive resin as a binder. , magnetic interlayer transition in the non-uniform part,
Bronching due to leaching of components in the magnetic coating film is less likely to occur, and it is possible to crosslink and polymerize by reaction with a polyvalent isocyanate group-containing compound without irradiating it with radiation, making it unnecessary to use an expensive electron beam irradiation system. The amount of polyvalent isocyanate required is less than when adding it to a thermosetting resin, and it is economical, has less influence on pot life, and provides a good magnetic recording medium with less friction. .

<Structure of the invention> That is, it includes a radiation-sensitive soft resin having a radiation-sensitive unsaturated double bond such as an acrylic double bond, a maleic double bond, an allylic double bond, or a prepolymer, oligomer, or telomer thereof. Instead of coating ferromagnetic fine particles on a carrier using a binder and crosslinking and polymerizing them with radiation, a crosslinking agent typified by a compound containing a polyvalent isocyanate group such as TDI or MDI is added to the binder to achieve the desired purpose. It is intended to achieve the following.

(1) Radiation sensitivity in a magnetic recording medium that is mainly composed of ferromagnetic fine particles and has radiation-sensitive unsaturated double bonds such as acrylic double bonds, maleic double bonds, and allyl double bonds as a binder. A mixture of a soft resin or its prepolymer, oligomer, or telomer and the above-mentioned radiation-sensitive modified resin having double bonds is used, and the mixing ratio of the two is adjusted to satisfy the properties shown below. and radiation-sensitive elastomer in a ratio of 2:8 rather than 8:2. The radiation-sensitized resin referred to here is 100 Hz in the state before radiation-sensitized.
The dynamic elastic modulus is 1.0 in the temperature range from 20℃ to 60℃
Those exhibiting X109dyn/cJt or more are particularly desirable. On the other hand, the radiation-sensitive solvent-plasticized elastomer refers to an elastomer, or its prepolymer, oligomer, or telomer, which has excellent rubber elasticity, flexibility, and adhesion to a polyester substrate as a synthetic rubber, and includes 10 (
The dynamic elastic modulus at l llz is 1 in the temperature range from 20°C to 60°C. Shows mechanical properties of less than OX109dyn/cJ.

As described later, these thermoplastic resins and solvent-soluble elastomers are subjected to radiation-sensitive modification in order to generate radicals and create a crosslinked structure by adding a crosslinking agent typified by a polyvalent isocyanate group-containing compound.

Further, it is desired that the plastic component after radiation-sensitized modification and the elastomer or its prepolymer, oligomer, or telomer have good compatibility from the viewpoint of dispersion of magnetic fine particles.

The use of binders that combine radiation-sensitive resin components and elastomer components to form a three-dimensional network structure through radiation irradiation can be used for a variety of applications such as audio, video, memory, and measurement. In addition to the electromagnetic conversion characteristics of magnetic recording media, various physical properties required of magnetic coatings include hardness, flexibility, abrasion resistance, an appropriate coefficient of friction, and no stick-slip phenomenon.

It is extremely effective in maintaining stability under various environmental conditions ranging from low to high temperatures and low to high humidity with various physical properties such as surface moldability, adhesion to base, elasticity modulus of 1 or more. Ta.

(2) In addition, if a general-purpose thermoplastic resin that does not have a radiation-sensitive double bond and is suitable for a magnetic tape binder is used instead of a radiation-sensitive modified resin, it will be possible to meet the requirements especially when using a magnetic tape. It is effective in imparting appropriate flexibility, and in practical terms, it improves the durability and reliability of repeated running under high temperature and high humidity conditions, and improves head touch to improve output in the short wavelength range by improving spacing loss between tape heads. and video S/N is improved.

In order to satisfy the properties shown below, the mixing ratio of the thermoplastic resin and the radiation-sensitive elastomer is particularly preferably 2:8 rather than 8:2.

In addition, in order for the thermoplastic resin to impart appropriate flexibility to the magnetic coating film, its molecular weight should be at least 5,000, preferably 8,000.
The above is necessary for the molecular weight effect.

On the other hand, radiation-sensitive solvent-soluble resins and elastomers are elastomers or elastomers that are obtained by crosslinking or polymerizing with radiation alone and have excellent rubber elasticity, flexibility, and adhesion to polyester substrates as synthetic rubbers. This solvent-soluble elastomer, which refers to prepolymers, oligomers, and telomers, is subjected to radiation-sensitive modification in order to generate radicals and create a crosslinked structure when exposed to radiation, as will be described later.

Further, it is desired that the thermoplastic resin and the radiation-sensitive elastomer or its prepolymer, oligomer, or telomer have good compatibility from the viewpoint of dispersing magnetic fine particles.

This invention relates to the above (1) or (2), or (1) and (
By further adding polyester into which a sulfonic acid metal base has been introduced to a mixture of both of the mixtures shown in 2), and performing the radiation treatment shown in (1) or (2) above, dispersibility and electromagnetic conversion characteristics can be improved. This provides an even more excellent magnetic recording medium.

3-1 Examples of the thermoplastic resin that does not have radiation-sensitive modified or radiation-sensitive double bonds used in the present invention include the following synthetic resins for coatings.

N) Vinyl chloride copolymer Vinyl chloride-vinyl acetate-vinyl alcohol copolymer (including maleic acid introduced type).

Vinyl chloride-vinyl alcohol, t=Ii combination (including maleic acid introduced type), vinyl chloride-vinyl acetate copolymer (including maleic acid introduced type), vinyl chloride-vinyl alcohol-vinyl propionate copolymer, chloride Vinyl-vinyl acetate-maleic acid copolymer 11-vinyl acetate-vinyl acetate-terminal OH side chain alkyl group copolymer, such as IJ CC Company VI? 01
1. VYNC.

VY [Knee-X, VYSM-X, VRRR, etc. (1) Saturated polyester resin phthalic acid, isophthalic acid, terephthalic acid, maleic acid,
Saturated polybasic acids such as maleic acid derivatives, succinic acid, adipic acid, and sebacic acid and ethylene glycol, diethylene glycol, glycerin 9, trimethylolpropane,
■, 2-propylene glycol, 1.3-butanediol,
Dipropylene glycol, 1.4 butanediol, 1.
6 hexanediol, pentaerythritol, tul-bitol, glycerin, neopentyl glycol, 1.4
Saturated polyester resin etc. obtained by ester bonding with polyhydric alcohol such as cyclohexane dimetatool.

(Ill) Unsaturated polyester resin A polyester compound containing a radiation-curable unsaturated double bond in its molecular chain, for example, consisting of an ester bond between a polybasic acid and a polyhydric alcohol as described as a thermoplastic resin in Section (TI) Examples include unsaturated polyester resins, prepolymers, and oligomers containing radiation-curable unsaturated double bonds in which part of the polybasic acid is maleic or acidic.

Examples of the polybasic acid and polyhydric alcohol components of the saturated polyester resin include the compounds listed in item (1), and examples of the radiation-curable unsaturated double bond include maleic acid,
Mention may be made of fumaric acid.

The radiation-curable unsaturated polyester resin is produced by a conventional method by adding maleic acid, fumaric acid, etc. to one or more polybasic acid components and one or more polyhydric alcohol components, that is, in the presence of a catalyst.
After dehydration or dealcoholization reaction at 200°C in a nitrogen atmosphere, the temperature is raised to 240-280°C and 0.5-l+v
A polyester resin can be obtained by a condensation reaction of aHg under reduced pressure. The content of maleic acid, fumaric acid, etc. in the acid component is 1 to 40 mol%, preferably 10 to 30 mol%, in view of crosslinking during production, radiation curability, etc.

(IV) Polyvinyl alcohol resin Polyvinyl alcohol, butyral resin, acetal resin, formal resin, and copolymers of these components also have good IL compatibility with magnetic powder. In this case as well, radiation sensitivity degeneration is performed if necessary.

(V) Epoxy resin, phenoxy resin Epoxy resin produced by the reaction of bisphenol A and epichlorohydrin or methylepichlorohydrin Shell Chemical! I! (Epicote 152.154,828, 1001.1004.
1007), manufactured by Dow Chemical (IIEN431, rlE
R732, DLR51LIIRI+ 331), Dainippon Ink (Ebikuron-400, Ebikuron-80
0), and phenoxy resin manufactured by UCC (PKII8, PKIIC, PKI), which is a high polymerization degree resin of the above epoxy.
Copolymer of former brominated bisphenol A and epichlorohydrin, manufactured by Dainippon Ink (Epicron 145°152
, 153.1120) etc. are also effective.

(VT) Cellulose Derivatives Cellulose derivatives of various molecular weights are also effective as thermoplastic components. Among them, particularly effective ones include nitrified cotton, cellulose acetobutyrate, ethyl cellulose, butyl cellulose, and acetyl cellulose.

Other thermoplastics include thermoplastic rigid polyurethane resins, polyether ester resins, polyvinylpyrrolidone resins and derivatives (PVP olefin copolymers), polyamide resins, polyimide resins, and phenolic resins.

Spiroacecool resin, acrylic resin containing at least one kind of hydroxyl group-containing acrylic ester and methacrylic ester as a polymerization component are also effective for the purpose of the present invention.

Radiation sensitivity changes when necessary.

(■) Polyester resin An example of a compound containing one or more hydroxyl groups is Adeca Polyether P-700. Polyfunctional polyethers such as Adeka Boriether P-1000, Acrylic Ester G-1500 (manufactured by Asahi Denka Co., Ltd.), Polymeg 1000, and Polymeg 650 (manufactured by Forker-Cola Co., Ltd.).

(■) Polycaprolactone An example is polycaprolactone PCP-2000
Polyfunctional polyesters such as polycaprolactone PCP-0240, polycaprolactone PCP-0300 (manufactured by Chisso Corporation), etc.

Other thermoplastic plastics include polyether ester resins, polyvinylpyrrolidone resins and derivatives (PVP olefin copolymers), polyamide resins, polyimide resins, phenolic resins, spiroacecool resins,
Acrylic resins containing at least one hydroxyl group-containing acrylic ester and methacrylic ester as a polymerization component are also effective for the purpose of the present invention, and their effects can be further enhanced by radiation-sensitive modification.

3-2 On the other hand, the radiation-sensitive soft resin or prepolymer to be combined with the thermoplastic resin or radiation-sensitive modified resin is as follows.

(1) Polyurethane elastomers and prepolymers and telomers Examples of such urethane compounds include, as isocyanates, 2.4-) luene diisocyanate-1, 2
．． 6-Toluene diisocyanate.

1.3-xylene diisocyanate, 1.4-xylene diisocyanate 1-, 1.5-naphthalene diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate, 3.3'-dimethyl-4.4
″-diphenylmethane diisoso-1,4,4′
-diphenylmethane diisocyanate, 3.3'
-dimethylbiphenylene diisocya*-I-,4,4'
- Various polyvalent isocyanates such as biphenylene diisocyanate, hexamethylene diisocyanate 1° isophorone diisocyanate, dicyclohexylmethane diisocyanate, Desmodur L, Desmodur N, linear saturated polyesters (ethylene glycol, diethylene glycol, chrycerin, methylolpropane,
1.4-Butanediol.

1.6-hexanediol, pentaerythritol.

With polyhydric alcohols such as sorbitol, neopentyl glycol, 1.4-cyclohexane dimetatool, and saturated polybasic acids such as phthalic acid, isophthalic acid, terephthalic acid, maleic acid, succinic acid, adipic acid, and sebacic acid. ), linear saturated polyethers (polyethylene glycol, polypropylene glycol, polytetraethylene glycol) and caprolactam 1 hydroxyl group-containing acrylic esters.

Polyurethane elastomers, prepolymers, and telomers made of polycondensates of various polyesters such as methacrylic acid esters containing hydroxyl groups are effective.

(n) Acrylonitrile-butadiene copolymer elastomer Synclair Petrochemical Co., Ltd. PolyBI) Acrylonitrile-butadiene copolymer prepolymer with a terminal hydroxyl group commercially available as Liquisotresin, or elastomer such as Hiker 1432, J manufactured by Nippon Zeon Co., Ltd. teeth,
It is particularly suitable as an elastomer component in which the double bond in butadiene generates radicals by electron beams and undergoes crosslinking and polymerization.

Furthermore, those having a terminal hydroxyl group are effective in further increasing radiation sensitivity by adding an acrylic double bond via diisocyanate or the like.

(ITI) Polybutadiene Elastomer A prepolymer having a low molecular weight terminal hydroxyl group, such as PolyBD Liquino Resin R-15 manufactured by Sinclair Petrochemical Co., is particularly suitable in terms of compatibility with thermoplastic plastics and affinity with magnetic powder. Since the R-15 prepolymer has a hydroxyl group at the end of the molecule, it is possible to increase the radiation sensitivity by adding an acrylic unsaturated double bond to the end of the molecule, making it even more advantageous as a binder.

In addition, polybutadiene cyclized product Nippon Synthetic Rubber Co., Ltd. CBR-
The old M9 also exhibits excellent performance when combined with thermoplastics. In particular, cyclized polybutadiene has high efficiency in crosslinking polymerization by radiation using radicals of unsaturated bonds inherent in polybutadiene, and has excellent properties as a binder.

Preferred geothermoplastic elastomer and prepolymer systems include chlorinated GoJ.

Acrylic rubber, isoprene rubber and its cyclized products (CIR701 epoxy modified rubber manufactured by Japan Synthetic Rubber Co., Ltd.).

Internally plasticized saturated linear polyester (Toyobo Byron #3
00) and the like are also effective in the present invention by subjecting them to the radiation sensitivity modification treatment described below.

3-3 Specific examples of the electrosensitive modification described above include acrylic acid, which exhibits an unsaturated double bond having radical polymerizability,
Groups that can be crosslinked or polymerized and dried by radiation irradiation, such as acrylic double bonds such as methacrylic acid or their ester compounds, allylic double bonds such as diallyl phthalate, and unsaturated bonds such as maleic acid and maleic acid derivatives. It is introduced into the molecule.

Any unsaturated double bond that undergoes cross-linking polymerization upon irradiation with radiation can be used.

(1) As a more specific method of radiation sensitivity modification, one molecule of the above thermoplastic resin or its prepolymer having one or more hydroxyl groups in the molecule is reacted with one or more molecules of isocyanate groups of a polyisocyanate compound, and then A reactant with one or more molecules of a monomer having a group that reacts with an isocyanate group and a radiation-curable unsaturated double bond, for example, per hydroxyl group of linear polycaprolactone PCP-2000 (manufactured by Chisso Corporation). A resin having at least 21 [1i1] acrylic double bonds at the terminal obtained by reacting one molecule of toluene diisocyanate with one molecule of 2-hydroxyethyl methacrylate, or a prepolymer or oligomer thereof.

One example is telomer.

In addition, the polyisocyanate compounds used here include 2.4-1-ruene diisocyanate, 2.6-)
luene diisocyanate, 1,3-xylene diisocyanate I, 1,4-xylene diisocyanate, m
-phenylene diisocyanate, p-phenylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, Desmodur L, Desmodur IL (manufactured by Bayer AG, West Germany), and the like.

Examples of monomers having a group that reacts with an isocyanate group and a radiation-curable unsaturated double bond include 2-hy-l-oxyethyl ester of acrylic acid or methacrylic acid;
-Esters having hydroxyl groups such as hydroxypropyl ester and 2-hydroxyoctyl ester; acrylamide.

Methacrylamide, N: An intermediate having an active hydrogen that reacts with an isocyanate group such as methylol acrylamide and containing an acrylic double bond; Furthermore, allyl alcohol, maleic acid polyhydric alcohol ester compound, unsaturated double bond Also included are monomers containing unsaturated double bonds that have active hydrogen that reacts with isocyanate groups, such as mono- or diglycerides of long-chain fatty acids that have radiation curability.

(11) 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 monomer having a group that reacts with the epoxy group and an electron beam curable unsaturated double bond, such as glycidyl methacrylate A resin or prepolymer in which acrylic double bonds are made pendant in the molecule by reacting acrylic acid with a thermoplastic resin containing epoxy groups obtained by radical polymerization of esters, and by ring-closing reaction between carboxyl groups and epoxy groups. Or oligomers, or resin 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.

Here, compounds containing one or more epoxy groups in the molecule include homopolymers of acrylic esters or methacrylic esters containing epoxy groups, such as glycidyl acrylate and glycidyl methacrylate, or copolymerizable with other polymerizable monomers. Epicoat 828 described in the section of plastic resin (V). Epicor [001, Epicor 1007. There are various other types of epoxy resins such as Epicoat 1009 (manufactured by Shell Chemical Co., Ltd.).

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

(III) 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 the carboxyl group and a radiation-curable unsaturated double bond, such as methacrylic acid. Glycidyl methacrylate is reacted with a thermoplastic resin containing a carboxyl group obtained by solution polymerization, and an acrylic double bond is introduced into the molecule through a ring-opening reaction between the carboxyl group and the epoxy group in the same manner as in Section 2. Examples include resins, prepolymers, and oligomers.

Here, as compounds containing one or more carboxyl groups in the molecule, polyester acids in the resins mentioned above containing carboxyl groups in the molecular chain or at the molecular end; acrylic acid 5
These include homopolymers of monomers having radical polymerizability and carboxyl groups, such as methacrylic acid, maleic anhydride, and fumaric acid, or copolymers with other polymerizable monomers.

Examples of the small polymer having a group that reacts with a carboxyl group and a radiation-curable unsaturated double bond include glycidyl acrylic L/-1., glycidyl methacrylate, and the like.

3-4 When using a solvent in the present invention, acetone,
Ketones such as methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; isocyanates such as methanol, ethanol, isopropanol, and citanol;
Alcohols that could not be used in heat curing, tetrahydrofuran, those with ether bonds such as thioxane, dimethylformamide, vinylpyrrolidone,
A solvent such as r1 propane, and an aromatic hydrocarbon diluent or solvent such as 1-toluene or xylene are used.

As substrates used for coating, polyethylene terephthalate films, which are currently widely used as substrates for magnetic recording media, and polyimide films, polyamide-imide films, etc., are used for applications that require further heat resistance, and in particular polyester In the case of thin films, axial stretching or biaxial stretching is often applied.

The magnetic fine powder utilized in the present invention is rFezos.

Fe, 04+Co doped r -Fe, 0. , Co-doped 7-Fe, 03-Pe 5% solid solution, Crk, G
o type compound adhesion type r -Fe, 03° Go type compound adhesion type Fej04 (includes intermediate oxidation state with γFe2O3. Also, the Co type compound mentioned here refers to cobalt oxide, cobalt hydrate, and cobalt ferrite.

A case is shown in which the magnetic anisotropy of cobalt, such as a cobalt ion adsorbent, is utilized in the coercive direction. ), also CO+Pe-Co,
The main component is a ferromagnetic metal element such as Fe-Co'-Ni+ Co-Ni. The manufacturing method is a wet reduction method using a reducing agent such as NaB114, or after treating the iron oxide surface with an St compound.
Examples include a dry reduction method using 1λ gas or the like, or a method obtained by vacuum evaporation in a low-pressure argon gas stream. Furthermore, single crystal barium ferrite fine powder can also be used.

The above-mentioned magnetic particles have an acicular or granular shape, and are selected depending on the intended use as a magnetic recording medium.

The radiation cross-linking type or radiation polymerization drying type of the present invention is used for high-bias old Fi audio cassette tapes, video cassette tapes, master tapes for video tape contact transfer printing, etc., which have undergone remarkable technological progress and marketability has expanded in recent years. By combining the binder with cobalt-modified acicular iron oxide (cobalt-doped type and cobalt-based compound coated type), which is particularly advantageous for high-density recording applications among the above magnetic fine powders, or acicular alloy fine particles with even higher coercivity, extremely good results can be obtained. We were able to obtain a high-performance tape with excellent electromagnetic conversion characteristics and reliable physical properties.

Regarding the radiation curing type or magnetic recording medium binder according to the present invention, various antistatic agents, lubricant 9 dispersants, coating film strength reinforcing additives, etc. used in the application may be appropriately utilized according to the application. is also valid.

Examples of polyvalent isocyanate-1 group-containing compounds used for crosslinking and polymerization of the binder of the present invention include tolylene diisocyanate (Tl11), cyphenylmethane diisocyanate-1-(M old), coronate, and coronate. +11. (manufactured by F1 Polyurethane Co., Ltd.).

Next, the present invention will be specifically explained with reference to Examples.

Examples: Synthesis example of radiation-sensitive binder a) Synthesis of acrylic modified urethane elastomer (electron-sensitive elastomer) Urethane prepolymer based on diphenylmethane diisocyanate (MDI) terminal isocyanate (Nisoborane 4040 manufactured by Nippon Polyurethane Co., Ltd.) 250 parts, 2-hydroxy 32.5 parts of ethyl methacrylate, 0.07 part of hydroquinone, and 0.009 part of tin octylate were placed in a reaction vessel and heated to 80°C and melted, followed by tolylene diisocyanate 43
．． 5 parts were added dropwise while cooling the reaction vessel to a temperature of 80 to 90°C, and after the completion of dropping, the NGO reaction rate was 95 at 80°C.
% or more.

b) Synthesis of acrylic modified polyether-based urethane-terminated elastomer (electrosensitive elastomer) Polyether PTG-500 manufactured by Nippon Polyurethane Co., Ltd.
250 parts, 211 parts MA, 32.5 parts, hydroquinone (1,007 parts, and 0.009 parts of tin octylate) were placed in a reaction can and heated to 80°C and dissolved, then 143.5 parts of TD was added until the temperature inside the reaction can was 80~ Drop it while cooling it to 90℃,
After the dropwise addition is completed, the reaction is allowed to proceed at 80° C. until the NGO reaction rate reaches 95% or more.

C) Synthesis of acrylic modified polybutadiene elastomer (electrosensitive elastomer) Low molecular weight terminal hydroxyl group polybutadiene polyBD Liquiso resin R-15250 manufactured by Sinclair Petrochemical Co.
parts, 211 parts MA 32.5 parts, hydroquinone 0.0
Put 0.07 parts and 0.009 parts of tin octylate into a reaction vessel.8
After heating and dissolving at 0°C, 43.5 parts of TDT was added dropwise while cooling the reaction vessel to a temperature of 80 to 90°C, and after the dropwise addition was completed, the mixture was allowed to react at 80°C until the NGO reaction rate reached 9.

d) Synthesis of polycaprolactam-based acrylic modified product POLYO-/1zpcp-0200 (polycaprolactone manufactured by Sennoson 1) 250 parts, 2-hydroxyethyl methacrylate 122.2 parts, hydroquinone 0.024 parts, tin octylate 0.033 parts was placed in a reaction can and heated to 80°C and dissolved, then 163.6 parts of TD1 was added to the reaction can at a temperature of 80°C.
The mixture is added dropwise while cooling to ~90°C, and after the dropwise addition is completed, the mixture is allowed to react at 80°C until the NGO reaction rate reaches 95% or more.

The molecular weight of this resin is 1140.

e) Synthesis example of unsaturated polyester EBC resin: 136 parts of dimethyl cehatate, 12.2 parts of dimethyl adipate,
Dimethyl maleate 64.8 parts, neopentyl glycol 73 parts, 1,6-hexanediol 74 parts, tetra-
Charge 0 parts of n-butyl titanium into a reaction vessel and perform a demethanol reaction at 180°C in a N2 stream at 240-260°C.
A condensation reaction was carried out under a reduced pressure of 0.1 to 11 Hg to obtain an internally plasticized resin close to an elastomer.

Example Cobalt-coated sword-shaped r Veto3 (long axis 0.4p.

Short axis 0.0511, lle 6000e) 12
0 parts by weight carbon blank (for antistatic use, to Mitsubishi carbon blank i-600)' 5 parts by weight to α-1. O6 powder (0.5μ granules) 2 parts by weight Dispersant (purified soybean lecithin) 3M parts I agent (methyl ethyl ketone/toluene 5 (1150) 100 parts by weight The above composition was mixed in a ball mill for 3 hours, and then mixed with a set magnetic oxidation agent. Iron can be moistened and removed using a dispersant.

Acrylic double bond introduced saturated polyester 161 resin (C)
10 parts by weight (calculated as solid content) Acrylic double bond-introduced white: bicopolymer (a) 10 parts by weight
parts (solid fraction w) Acrylic double bond-introduced polyether urethane elastomer (f) 10 parts by weight (solid content equivalent) Solvent (methyl ethyl ketone/toluene 50150) 200 parts by weight Lubricant (higher fatty acid modified silicone oil) 3 parts Quantity Mix and dissolve the above binder mixture well. This was put into the ball mill where the magnetic powder was treated earlier and again
Mix and disperse for 22 hours. 5 parts by weight (in terms of solid content) of an isocyanate compound (coronate) that can react with and crosslink with the functional groups, mainly hydroxyl groups, of the binder in the post-dispersion paint were mixed for 20 minutes into the double ball milled paint. Ta.

Apply magnetic paint on a 15μ polyester film,
After orientation on a permanent magnet (1600 gauss) and drying the solvent with an infrared lamp or hot air, and after surface conditioning treatment, the roll was kept in an oven maintained at 80°C for 48 hours to promote crosslinking reaction by isocyanate. .

The resulting tape was cut into 2-inch pieces to obtain a videotape (sample #1).

The acrylic double bond-introduced vinyl chloride/vinyl alcohol copolymer used here was synthesized according to the following procedure.

1) Vinyl chloride used as a raw material in Examples.

The vinyl alcohol copolymer was prepared by the following synthesis method.

Manufacturing method of vinyl chloride and vinyl alcohol copolymer A vinyl chloride-vinyl acetate copolymer with a ratio of 75/25 (vinyl chloride group/vinyl acetate group) and an average degree of polymerization n=400 is used as a raw material, and this is used as the former BK ( 7. Suspended in a mixed dispersion medium of a solvent such as methyl isobutyl ketone and water, and stirred 11.
By mechanical dispersion using 3L in 2 machines, etc., a suspension similar to a slurry is made by moistening the resin.

Next, add iQ sodium methylate to this.
The acetyl group of vinyl acetate is saponified into a hydroxyl group by adding it as a 1+ medium and keeping the temperature around )) 0°C.

In addition, a stabilizer to prevent dehydrochlorination or a suspending agent to uniformly suspend the solution may be used.

Next, 1lli1' acid and FIl! are generated from the eliminated acetyl group. ! The medium was removed by washing the saponified slurry with water, and the stable 4Bi fat I11 was removed by r+;
Melt. In this case, a decoloring step for removing chlorine ions and the like may be added, if necessary, in order to eliminate coloration during saponification.

The properties of the hynyl chloride/vinyl alcohol 1-al copolymer obtained by the saponification method described above were as follows.

Vinyl chloride group 87% Vinyl acetate group 0.3% or less Vinyl alcohol group 12.6% Degree of polymerization 330 750 parts of the above vinyl chloride, vinyl alcohol copolymer, 1250 parts of toluene, 500 parts of cyclohexanone, 5β
4 parts were placed in a flask, heated and dissolved, and after raising the temperature to 80°C, 61.4 parts of 2-hydroxyethyl methacrylate adduct of tolylene diisocyanate was added, and further 0.012 part of tin octylate was added, and the NCO reaction rate was determined at 80°C in a N2 stream. After completion of 90% or more, the mixture was cooled and diluted by adding 1250 parts of methyl ethyl ketone.

Comparative Example In the example, the obtained magnetic paint was coated on a 15μ polyester film after 42 hours of mixing and dispersion in a ball mill without mixing the crosslinking isocyanate compound,
After orientation on a permanent magnet (1600 gauss), drying the solvent with an infrared lamp or hot air, and surface smoothing treatment, an acceleration voltage of 150 KV and electrode Current 10m
A. The coating film was cured by irradiation with an electron beam in an N2 atmosphere at an absorbed dose of 0.5 and 5 Mrad.

The resulting tape was cut into 2-inch pieces to obtain a videotape (sample #2).

When using the samples of the above Examples and Comparative Examples, the video sensitivity at 4Ml1z of the obtained videotape was compared with the equipment time after applying the magnetic paint until the surface smoothing treatment was not performed during the videotape production process. The level is shown on the drawing.

The sensitivity was determined by using the output of the videotape at 4Ml1z when the surface was smoothed immediately after application as QtlB, and thereafter tracking changes in surface workability over time.

As shown in the graph in Figure 1, the effect of BoI-life is small, only a small amount of polyvalent isocyanate-1 is required, and an expensive electron beam irradiation system is not required.
Decreased dimensional stability due to thermal deformation of the base material of magnetic recording media such as polyester film when thermosetting resin is used, magnetic interlayer transition in non-uniform areas, and blocking due to seepage of components in the magnetic coating film. etc., and a good magnetic recording medium with low friction was obtained.

Although the present invention has been variously explained above with reference to preferred embodiments, the present invention is not limited to these embodiments, and many modifications may be made within the scope of the present invention without departing from the spirit of the invention. Of course.

[Brief explanation of drawings]

The drawing shows the level of sensitivity of the video tape in relation to the time taken by the equipment after applying the magnetic paint until the surface smoothing process is applied during the videotape production process, and the influence of pot life can be seen. Patent applicant TDC Co., Ltd. Representative Hiroshi Otoshi

Claims (1)

[Claims] 1. A radiation-sensitive soft resin having a radiation-sensitive unsaturated double bond such as an acrylic double bond, a maleic double bond, an allylic double bond, or a prepolymer, oligomer, or telomer thereof and at least one of the above-mentioned radiation-sensitive modified resin having a double bond and a thermoplastic resin not having a radiation-sensitive double bond as a binder, ferromagnetic fine particles as a main component, and isocyanate added. A magnetic recording medium characterized by being crosslinked and polymerized by. 2. The magnetic recording medium according to claim 1, wherein acicular cobalt-modified magnetic iron oxide and/or alloy magnetic powder is used as the ferromagnetic fine particles.