JPH02201725A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a magnetic recording medium having excellent properties in heat resistance, adhesion to a supporting body, durability, wear resistance, etc., by providing a magnetic layer containing a specific binder on the supporting body comprising stylene polymers. CONSTITUTION:The magnetic layer in which a curing-type phosphazen compd. is incorporated as the binder for the magnetic material is provided on the supporting body comprising stylene polymers essentially having syndiotactic structure. The stylene polymer essentially having syndiotactic structure is suitable for the supporting body of magnetic recording medium as it has excellent heat resistance and mechanical strength. The specific phosphazen compd. having curing-type polymerizable groups satisfies all properties required for a binder. Thereby, the obtd. medium has large adhesion strength to the supporting body, high tensile elasticity, excellent properties in heat resistance, wear resistance, solvent resistance and good dispersion of the magnetic material component.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magnetic recording medium, and more particularly to a magnetic recording medium that has excellent durability, heat resistance, etc. and is used as a magnetic tape, magnetic card, magnetic disk, etc.

[Prior art and problems to be solved by the invention] In general, magnetic recording media such as video magnetic tapes, recording magnetic tapes, computer magnetic tapes, magnetic disks, magnetic drums, and magnetic cards are made of γ-iron oxide or the like. It is manufactured by applying a magnetic composition containing a magnetic material to a support such as a plastic film, disk, or card, and forming a magnetic layer on the surface thereof.

Conventionally, polyethylene terephthalate (PET) films have been used as these supports, but they do not have sufficient heat resistance and may become unable to extract information from the medium due to deformation (stretching) of the support.

Further, one of the requirements for the tape support is mechanical strength. As the reliability of the tape running system of a tape recorder increases, as the total thickness of the tape decreases, and as the recording density becomes higher and narrower, the mechanical strength of the tape support must be improved. It is strongly requested. In particular, when considering runnability and practical durability, the "stiffness" of the tape itself, that is, the properties related to its elastic modulus, and the surface hardness of the support itself to reduce friction are important.
Conventional materials using PET film as a support do not have sufficient characteristics such as these, and improvements are desired.

Furthermore, a binder is blended into the magnetic composition in order to make the magnetic body stick (adhere) to the support. As such binders, acrylic resins, ester resins, epoxy resins, urethane resins, isocyanate resins, and silicone resins have been known, but magnetic The layer not only has insufficient adhesion (adhesiveness) to the support, but also has insufficient durability and abrasion resistance, as well as poor solvent resistance.

The present inventors have conducted extensive research in order to develop a magnetic recording medium that is excellent in various performances such as heat resistance, adhesion to a support, durability, and abrasion resistance.

[Means to solve the problem]

As a result, it was found that styrenic polymers mainly having a syndiotactic structure are suitable for magnetic recording media as supports with excellent heat resistance and mechanical strength, and that specific phosphazene compounds having polymerizable curable groups are suitable as binders. It was found that this material satisfies all of the desired performance. The present invention was completed based on this knowledge.

That is, the present invention provides a magnetic recording medium characterized by having a magnetic layer containing a curable phosphazene compound as a binder on a support mainly made of a styrene polymer having a syndiotactic structure.

In the magnetic recording medium of the present invention, a support mainly made of a styrene polymer having a syndiotactic structure is used. Here, a syndiotactic structure is mainly a syndiotactic structure in which the stereochemical structure is mainly a syndiotactic structure, that is, the phenyl groups or substituted phenyl groups that are side chains are arranged in opposite directions alternately with respect to the main chain formed from carbon-carbon bonds. It has a three-dimensional structure, and its toughness is determined by nuclear magnetic resonance method (1" C-NMR method) using carbon isotope. can be expressed by the abundance ratio of a plurality of consecutive structural units, for example, a diad in the case of two, a triat in the case of three, and a pentad in the case of five, but mainly syndiotactic structure as referred to in the present invention. A styrenic polymer having a styrenic polymer is 75% or more for diad, preferably 85% or more for continuous chamber, or 30% or more for pentad (racemic pentad), preferably 50% or more.
Polystyrene, poly(alkyl styrene), poly(halogenated styrene), poly(alkoxystyrene), poly(vinyl benzoic acid ester), and mixtures thereof, or having these as main components, having a syndiotacticity of % or more Refers to copolymers. Here, poly(alkylstyrene) includes poly(methylstyrene) poly(ethylstyrene), poly(isopropylstyrene), poly(tert-butylstyrene), etc., and poly(halogenated styrene) includes poly((halogenated styrene)). These include chlorostyrene), poly(bromostyrene), and poly(fluorostyrene). Furthermore, examples of poly(alkoxystyrene) include poly(methoxystyrene) and poly(ethoxystyrene). Among these, particularly preferred styrenic polymers include polystyrene, poly(
p-methylstyrene) poly(m-methylstyrene),
Poly(p-tert-butylstyrene), poly(p-chlorostyrene), poly(m-chlorostyrene) poly(p-chlorostyrene)
-fluorostyrene), and furthermore copolymers of styrene and p-methylstyrene (JP-A-61
-187708).

Further, the molecular weight of the styrene polymer used in the present invention is not limited, but those having a weight average molecular weight of 50,000 or more are preferable, and those of 100,000 or more are particularly optimal. Further, there is no restriction on the width or narrowness of the molecular weight distribution, and various types can be used. This styrenic polymer mainly having a syndiotactic structure has a melting point of 160 to 310°C,
It has much better heat resistance than conventional styrene-based polymers with an active structure.

Such styrenic polymers having a mainly syndiotactic structure can be produced by using a titanium compound and a condensation product of water and trialkylaluminum as catalysts, for example, in an inert hydrocarbon solvent or in the absence of a solvent. It can be produced by polymerizing monomers (monomers corresponding to the above-mentioned styrenic polymers).

Commonly used thermoplastic resins, inorganic fillers, antioxidants, nucleating agents, plasticizers, compatibilizers, colorants, antistatic agents, and the like can be added to this styrenic polymer.

There are various antioxidants, but especially monophosphites and diphosphites such as tris(2,4-di-t-butylphenyl) phosphite and tris(mono- and di-nonylphenyl) phosphite. Phosphorous antioxidants and phenolic antioxidants are preferred. The diphosphite has the following general formula: [wherein R1 and R2 each represent an alkyl group having 1 to 2 carbon atoms, a cycloalkyl group having 3 to 20 carbon atoms, or an aryl group having 6 to 20 carbon atoms. ] It is preferable to use a phosphorus compound represented by the following.

Specific examples of the phosphorus compound represented by the above general formula include distearyl pentaerythritol diphosphite;
Dioctylpentaerythritol diphosphite; diphenylpentaerythritol diphosphite; bis(2
,4-di-L-butylphenyl)pentaerythritol diphosphite; bis(2,6-di-t-butyl-4-
Methylphenyl) pentaerythritol diphosphite; dicyclohexyl pentaerythritol diphosphite, and the like.

In addition, known phenolic antioxidants can be used, and specific examples thereof include 2,6-di-butyl-4-methylphenol; 2,6-diphenyl-4-methoxyphenol; .2'-methylenebis(6-t-butyl-4-methylphenol);2,2'
-methylenebis(6-L-butyl-4-methylphenol);2゜2''-methylenebis[4-methyl-6-(α
-methylcyclohexyl)phenol] 1ll-bis(5-t-butyl-4-hydroxy-2-methylphenyl)butane;
-cyclohexylphenol); 2.2”-methylenebis-(4-methyl-6-tunylphenol); L t
, 3-) lis-(5-t-7” thyl-4-hydroxy-
2-methylphenyl)butane; 2,2-bis-(5-t
-butyl 4-hydroxy-2-methylphenyl)-4-
n Dodecylmercaptobutane; ethylene glycol-bis[3,3-bis(3-mo-butyl-4-hydroxyphenyl)butyrate)il-1-bis(3,5-dimethyl-2-hydroxyphenyl)3-(n -dodecylthio)
-Butane; 4,4"thiobis(6-t-butyl-3-methylphenol), 1,3.5-)lis(3,5-di-t-butyl-4-hydroxybenzyl)-2,4,6 trimethylbenzene ;2,2-bis(3,5-di-t-butyl-4-hydroxybenzyl)malonic acid dioctadecyl ester;n-octadecyl 3-(4-hydroxy-3,
Examples include 5-di-t-butylphenyl) propionate; tetrakis[methylene (3,5-di-butyl-4-hydroxyhydrocinnamate)]methane.

The above antioxidant is based on 100 parts by weight of the styrenic polymer mainly having a syndiotactic structure.
It is blended in a proportion of 0.0001 to 2 parts by weight, preferably 0.001 to 1 part by weight.

If the blending ratio of the antioxidant is less than 0.0001 part by weight, the molecular weight will be significantly lowered, while if it exceeds 2 parts by weight, the mechanical strength will be affected, so both are not preferred.

Examples of thermoplastic resins include polystyrene with an acute structure, polystyrene with an acute structure, styrene polymers such as AS resin and ABS resin, polyesters such as polyethylene terecrate, and polycarbonate.

Polyethers such as polyphenylene oxide, polysulfone, and polyethersulfone; condensation polymers such as polyamide, polyphenylene sulfide (PPS), and polyoxymethylene; acrylic polymers such as polyacrylic acid, polyacrylic acid ester, and polymethyl methacrylate; Polyethylene, polypropylene, polybutene, polyolefin such as poly4-methylpentene-1, ethylene-propylene copolymer, or polyvinyl chloride.

Examples include halogen-containing vinyl compound polymers such as polyvinylidene chloride and polyvinylidene fluoride.

Furthermore, the inorganic filler may be fibrous, granular, or powdery. Glass fiber and carbon fiber are used as fibrous inorganic fillers.

Examples include alumina fiber. On the other hand, talc and carbon black are used as granular and powdery inorganic fillers.

Examples include graphite, titanium dioxide, silica, mica calcium carbonate, calcium sulfate, barium magnesium carbonate, magnesium sulfate, barium sulfate, oxysulfate, tin oxide, alumina kaolin, silicon carbide, metal powder, and the like.

These inorganic fillers significantly affect the film surface due to their particle shape, particle size, etc., so the particle size is usually 1/10 or less, preferably 1/20 of the film thickness.
It is preferable to select them so as to obtain the surface retention properties and physical properties according to the purpose, and it is also possible to use a mixture of two or more kinds.

The support used in the present invention is obtained by molding the above-mentioned styrene polymer or a composition containing the polymer and, if necessary, various additives, into the shape of a film, tape, disk, card, or the like. The thickness of these supports can be appropriately selected depending on the purpose, but when the support is in the form of a film, it is generally 1 to 100 μm, preferably 3 to 80 μm.
It has a thickness of m. Further, this film may or may not be stretch-molded. Large amounts of inorganic fillers for stretch-formed products.

Those containing incompatible resins or rubber are not preferred.

On the other hand, when used without stretch molding, inorganic fillers and resins are used in consideration of mechanical properties and heat resistance.

It is preferable to sufficiently incorporate rubber and the like.

Stretched films are produced by the method described in Japanese Patent Application No. 63-3847, specifically, by melting a styrene polymer mainly having a syndiotactic structure at a temperature above its melting point and then rapidly cooling it to form an amorphous raw material. It is obtained by creating a countersheet and then stretching the sheet at a temperature above the glass transition temperature and below the melting point. The quenching rate at this time is not particularly limited, but is generally set in the range of 200°C/sec to 3°C/sec, preferably 200°C/sec to 5°C/sec. Further, the dimensional stability and heat resistance of this stretched film can be further improved by heat treating it at a temperature not lower than the glass transition temperature and not higher than the melting point. The heat treatment time and temperature here are determined by the stretching ratio and thickness of the stretched body.

It can be appropriately selected in consideration of the composition, intended use, physical properties, etc. In general, above the glass transition temperature,
Although 1 second to 100 hours is possible at a temperature below the melting point, a range of 5 seconds to 30 minutes at a temperature from 20° C. higher than the glass transition temperature to 5° C. lower than the melting point is suitable. Below the glass transition temperature, there is no heat treatment effect, and above the melting point, part or all of the film will melt during heat treatment.

The stretching ratio during this stretching is preferably 3 times or more in area ratio (i.e., the area ratio of the stretched film to the original sheet), and more preferably 6 times or more, taking into consideration the mechanical properties of the film. be.

The amorphous original fabric obtained by cooling may be either cylindrical or planar, and may be stretched simultaneously or sequentially with gas (ie, inflation, blow molding) or with a tenter.

In addition, when a cylindrical die is used, stretching can be performed immediately after melting at a temperature higher than the glass transition temperature and lower than the melting point.

The magnetic recording medium of the present invention has a magnetic layer containing a curable phosphazene compound as a binder on the support as described above.

As a curable phosphazene compound, general 2% NP
(X)p(Y)q→−... [I] (in the formula, p, q
is p>0. It represents a real number satisfying q>0 and p+q=2, X represents a polymerizable curable group, and Y represents a polymerizable curable group or a non-polymerizable curable group. X and Y may be the same or different. ) A phosphazene compound having a repeating unit represented by the following formula and a degree of polymerization of 3 or more is suitable. Here, general formula [I]
does not represent a single compound, but represents the average value of a mixture of several compounds. therefore,
p and q indicating the number of each group are not necessarily limited to integers but are real numbers including decimal numbers. Similarly, the degree of polymerization is a real number including not only an integer of 3 or more but also a decimal number.

There are various phosphazene compounds having the repeating unit of the above general formula [■] depending on the type of each substituent. In the formula, It is a group having a reactive double bond. There are various types of groups having this reactive double bond, such as an acrylic group.

Examples include functional groups containing methacrylic, vinyl, or allyl groups, preferably acryloyloxy and methacryloyloxy groups.

Functional groups containing such acryloyloxy groups and methacryloyloxy groups include acryloyloxy groups and methacryloyloxy groups themselves, as well as representative examples thereof as shown in the general formula [wherein R3 represents a hydrogen atom or a methyl group, R4 is an alkylene group having 1 to 12 carbon atoms (preferably 1 to 3) (
(contains a branched alkylene group). ] It is expressed as. Specific examples of the group represented by the general formula [■] include 2-hydroxyethyl methacrylate 2-hydroxyethyl methacrylate 2-hydroxybutyl methacrylate 3-hydroxybutyl methacrylate 4-hydroxybutyl methacrylate
5-hydroxypentyl methacrylate, 6-hydroxy 3-methylhexyl methacrylate, 5-hydroxyhexyl methacrylate, 3-hydroxy 2-t-butylpropyl methacrylate 3-hydroxy-22-dimethylhexyl methacrylate, 3-hydroxy-2-
Methyl-2-ethylpropyl methacrylate and T2
- Residues obtained by removing hydrogen atoms from hydroxyl groups in methacrylates such as hydroxydodecyl methacrylate, and 2
Hydroxyethyl acrylate, 2-hydroxypropyl acrylate 2-hydroxybutyl acrylate
3-hydroxybutyl acrylate, 4-hydroxybutyl acrylate, 5-hydroxypentyl acrylate, 6-hydroxy 3-methylhexyacrylate, 5
-Hydroxyhexyl acrylate, 3-hydroxy-
2t-Butylpropyl acrylate 3-hydroxy-
Examples include residues obtained by removing a hydrogen atom from a hydroxyl group in acrylates such as 2,2-dimethylhexyl acrylate, 3hydroxy-2-methyl-2-ethylpropyl acrylate, and 12-hydroxydodecyl acrylate. Particularly preferred groups are 2-hydroxyethyl methacrylate residues and 2-hydroxyethyl acrylate residues.

Furthermore, as a functional group containing an allyl group, in addition to the allyl group itself, for example, an allyloxy group (CH2=CH-CH
20-) and allylamino group (CH2= CHCH2N
H) etc. Vinylphenol is a functional group containing a vinyl group.

Examples include residues obtained by removing a hydrogen atom from a hydroxyl group or an amide group in a compound containing a vinyl group such as vinyl sulfonamide.

On the other hand, Y in general formula (I) represents a polymerizable curable group or a non-polymerizable curable group. Here, when Y represents a polymerizable curable group, examples of the polymerizable curable group include those mentioned above (however, it may not be the same as X). Further, when Y represents a non-polymerizable curable group, there are various types of non-polymerizable curable group, and there is no particular restriction. Specifically, halogen atoms (chlorine atoms, bromine atoms, etc.), phenoxy groups, halogenated phenoxy groups (p-chlorophenoxy groups, etc.), alkoxy groups having 1 to 1 carbon atoms (methoxy groups, ethoxy groups, etc.), carbon atoms 1-1° halogenated alkoxy group (chloromethoxy group.

(chloroethoxy group, etc.), amino group, hydroxyl group, nitro group, etc.

In the magnetic recording medium of the present invention, the phosphazene compound used as the binder has the repeating unit of the above-mentioned general formula (1), and its degree of polymerization is 3 or more, preferably in the range of 3 to 18, particularly preferably 3 or 4. In addition, there are some units in which the repeating units of general formula (1) are bonded (polymerized) in a chain, but preferably they are bonded (polymerized) in a cyclic manner.
This is what I did.

A specific example of a phosphazene compound having a repeating unit of general formula CI) is a cyclic compound represented by:

cyclic compound represented by formula %formula% A cyclic compound represented by

formula %formula%) cyclic compound represented by formula %formula%) cyclic compound represented by formula %formula%)] A cyclic compound represented by

formula There are cyclic compounds that can be used as a material.

The above phosphazene compounds can be produced by various methods. For example, hydroxyalkyl (meth)acrylate represented by the general formula % formula % (wherein R' and R' are the same as above) and phosphonitrile chloride (chlorobosphazene; formula (N P Cfi
2). A cyclic compound represented by or the formula cz4p・(
By reacting with a chain compound represented by N P Cj22), 1-I N P Cl 3, where n is 3 or more, phosphonitrile chloride is completely substituted with the above-mentioned hydroxyalkyl (meth)acrylate residues. A phosphazene compound can be obtained.

Moreover, allyl alcohol allylphenol acrylamide b or the like can also be used instead of or together with the above hydroxyalkyl (meth)acrylate.

Further, in order to obtain a product in which Y in the general formula (1) is a non-polymerizable curable group, for example, when Y is a chlorine atom, it is sufficient that some of the chlorine atoms remain in the above reaction. In addition, when Y is a non-polymerizable curable group other than a chlorine atom, the chlorine atom bonded to the phosphorus atom in the phosphonitrile chloride of phenols, alcohols, amines, etc. is substituted in the above reaction. It can be produced by the presence of a compound having a functional group capable of absorbing water.

In addition, in the above reaction, it is preferable to use a dehydrohalogenating agent such as a tertiary amine.

Examples of the tertiary amine include trimethylamine, triethylamine, triisopropylamine, tri-n-propylamine, tri-n-butylamine, pyridine, and N,N,N-tetraethylenediamine, among which pyridine and triethylamine are preferred. It is.

Moreover, this reaction is usually carried out in an organic solvent that does not contain water. The organic solvent used is Hensen, toluene,
Examples include xylene, chloroform, cyclohexane, methylene chloride, and tetrahydrofuran. These can be used alone or in combination.

The magnetic recording medium of the present invention uses the phosphazene compound having the repeating unit of general formula [I] obtained as described above as a binder. A known method may be used to manufacture a magnetic recording medium using this binder. For example, iron oxides (T-iron oxide, triiron tetroxide, etc.), cobalt-containing T-iron oxide, chromium oxide, pure iron,
100 parts by weight of a magnetic material such as an iron-based alloy (such as a cobalt-iron-nickel alloy) or a nickel-cobalt alloy, 10 to 50 parts by weight of the above-mentioned binder, and a suitable solvent such as benzene, toluene, methyl ethyl ketone, cyclohexanone, or alcohol ( Add 100 to 300 parts by weight of a diluent), and further add 2 to 15 parts by weight of an antistatic agent, 2 to 15 parts by weight of a lubricant, 2 to 7 parts by weight of an abrasive, and 5 to 10 parts by weight of a dispersant. This is thoroughly kneaded using a ball mill or the like, and the resulting magnetic composition (magnetic paint) is applied to the above-mentioned supports (films, tapes, cards, etc.).

disc, etc.) and activate energy rays (ultraviolet rays, ultraviolet rays,
The magnetic layer is cured by irradiation with visible light, electron beams, X-rays, gamma rays, etc.) or by heating.

In addition, when using the above-mentioned curing method using active energy rays, a reaction initiator (photosensitizer) can also be used. Xylphenyl ketone, dibenzoyl, benzoyl, benzoyl methyl ether, benzoylethyl ether.

Examples include p-chlorobenzophenone, p-methoxybenzophenone, benzoyl peroxide, di-t-butyl peroxide, and camphorquinone, and these can be used alone or in combination.

In this case, the amount of the reaction initiator to be used is usually selected within the range of 0.05 to 5.0 parts by weight per 100 parts by weight of the phosphazene compound.

In addition, when using heat curing or room temperature curing methods,
As the polymerization initiator, peroxide compounds and amine compounds are usually used alone or in combination. Examples of peroxide-based compounds include benzoyl peroxide; p-chlorobenzoyl peroxide; 2,4-dichlorobenzoyl peroxide; t-butyl hydroperoxide; di-butyl peroxide; dicumyl peroxide; t-butyl peroxyacetate; t
-butyl peroxybenzoate and the like. In addition, examples of amine compounds include N, N-
Jetanol-p+-)shiidine; dimethyl-p-toluidine; P-)shiidine; methylamine; t-butylamine; methylethylamine; diphenylamine; 4,4
'-Dinitrodiphenylamine;0-nitroamine; p
-bromoaniline, 2,4.6-)ribromoaniline, and the like.

In this case, the total amount of the peroxide-based compound and the amine-based compound to be used may be selected in the range of 0.05 to 5.0 parts by weight, based on 100 parts by weight of the phosphazene compound.

Furthermore, the magnetic composition may contain other reactive curable compounds. Examples of reactive curing compounds that can be used here include methyl acrylate; hydroxyethyl acrylate; ethylene glycol diacrylate;
Diethylene glycol diacrylate; mixture of triethylene glycol diacrylate and tetraethylene glycol diacrylate with methacrylate nigericidyl acrylate, 2,2'-bis(acryloxyphenyl)propane, 2,2'-bis[4(3-methacryloxy) )-2-hydroxypropoxyphenyl]propane; vinyl esters of carboxylic acids (vinyl acetate, vinyl stearate, etc.) and ethylenically unsaturated dicarboxylic acids (fumaric acid, maleic acid, maleic anhydride, itaconic anhydride, etc.) can be mentioned.

The magnetic recording medium of the present invention thus obtained has various advantages such as excellent heat resistance and good adhesion between the magnetic layer and the support. Note that this magnetic recording medium can also be provided with a back coat layer if desired.

〔Example〕

Next, the present invention will be explained in more detail with reference to Examples and Comparative Examples.

Production Example 1 (Production of phosphazene compound) 2I! Hexachlorocyclotriphosphazene (formula (
86.8 g of a cyclic compound of NPCnz)+ was dissolved in 338 g of dehydrated benzene.

To this benzene solution were added 110 g of sodium carbonate, 155 g of pyridine, and 0.23 g of hydroquinone, and the mixture was stirred in a nitrogen stream.

Separately, 200 ml of 2-hydroxyethyl methacrylate was dissolved in 231 ml of benzene, and this solution was added dropwise into the above flask and reacted at 50°C for 6 hours. After the reaction, pyridine hydrochloride and sodium carbonate were removed by filtration.

The filtrate was washed with water, then dried using Glauber's salt, and the solvent was removed by vacuum distillation to give a viscosity of 1.1°, 3.3, 5.
5-hexa(methacryloylethylenedioxy)cyclotriphosphazene H3 (Formula (NP (OC,H40□CC=CH2)2)3
200 g (yield: 88.3%) of a cyclic phosphazene compound represented by

Production Example 2 (Production of polystyrene (SPS) having a syndiotactic structure) In a reaction vessel, 21 toluene as a solvent, 1 mmol of cyclopentadienyl titanium trichloride as a catalyst acid = 28 minutes, and 0.0 mmol of methylaluminoxane as an aluminum atom. 8 mol was added, 3.62 mol of styrene was added thereto at 20°C, and a polymerization reaction was carried out for 1 hour.

After the reaction was completed, the product was washed with a hydrochloric acid-methanol mixture to decompose and remove the catalyst component. It was then dried to obtain 330 g of a styrene polymer (polystyrene, sps). Next, this polymer was subjected to Soxhlet extraction using methyl ethyl ketone as a solvent to obtain an extraction residue of 95% by weight. The weight average molecular weight of this product is 290,000, and the number average molecular weight is 15.
8,000, and the melting point was 270°C. Also,
This polymer was analyzed by I30-NMR (solvent=1.
2 dichlorobenzene), absorption was observed at 145.35 ppm due to the syndiotactic structure, and the syndiotacticity in racemic pentad calculated from the peak area was 96%. Production example 3 (SPS
(Manufacture of a film consisting of) SP obtained in Reference Example 2 above
S, as antioxidants, bis(24-di-butylphenyl)pentaerythritol diphosphite and tetrakis[methylene(3,5-di-t-butyl-4-hydroxyhydrocinnamate)]methane were added to
．． 1 part by weight was mixed and extruded using a single screw extruder with a diameter of 40 mm to form pellets.

The obtained pellets were supplied to a device equipped with a T-die at the tip of a single-screw extruder with a diameter of 40 mm, and the cylinder temperature was maintained at 30 mm.
Extruded under the conditions of 0°C, T temperature 310°C, wall thickness 2
A sheet of 50 μm was obtained. At this time, the surface temperature of the sheet cooling roll was 30°C.

The raw sheet for stretching thus obtained was transparent, had a density of 1.04 g/cnt, a glass transition temperature of 100° C., and a crystallinity of 2%.

Next, this sheet was stretched 3 times lengthwise and crosswise at a stretching temperature of 120°C.
Simultaneous stretching was performed 5 times each. The obtained stretched film was fixed to a grid-shaped fixture and heat-treated at 250°C for 30 seconds. The thickness of the film at this time was 20 μm.

Example 1 400 parts by weight of γ-iron oxide (γ-Feze3) powder 150 parts by weight of the phosphazene compound obtained in Production Example 1, 4 parts by weight of carbon black, 10 parts by weight of silicone oil, 6 parts by weight of lecithin, 450 parts by weight of methyl ethyl ketone and 450 parts by weight of toluene were kneaded in a ball mill for 50 hours to obtain a magnetic composition.
A magnetic layer was formed by coating on a 0 μm SPS film so that the film thickness after drying was 5 μm.

Next, after drying at 90°C, 200 kiloelectron volts (Ke
V), the magnetic layer was hardened by irradiation with an electron beam having a dose of 6 megarads (Mrad) to produce a magnetic recording medium.

Various physical properties of the obtained magnetic recording medium were measured.

The results are shown in Table 1.

Comparative Example 1 Instead of the SPS film in Example 1, a thickness of 20 μm was used.
A magnetic recording medium was obtained in the same manner as in Example 1, except that a polyethylene terephthalate film of m was used.

Table 1 shows the measurement results of various physical properties.

Comparative Example 2 (1) Polyester diol (number average molecular weight 2500, OH
This was reacted with tolylene diisocyanate to obtain a urethane polymer, and further subjected to an addition reaction with 2-hydroxyethyl acrylate to obtain a polymer (number average molecule: 1t28,000).

(2) In Example 1, the same operation as in Example 1 was performed except that the polymer obtained in (1) above was used in place of the phosphazene compound of Production Example 1. The results are shown in Table 1.

(The following is a margin) * 1 * 2 * 3 * 4 * 5 After attaching cellophane tape to the tape surface, evaluation was performed when it was strongly peeled directly above.

○: No peeling, △: Partially peeled Gauze soaked with methyl ethyl ketone and evaluated by the number of times it was rubbed until the support appeared.

In accordance with JIS K 7204, the surface was rubbed with an abrasion wheel, and evaluation was made based on the difference in weight before and after rubbing.

The surface state of the magnetic layer was observed using a scanning electron microscope at a magnification of 2000 times.

◎...Very good, ○...Good The condition was observed after being left in an environment with a temperature of 80°C5 and 80% for 5,000 hours.

○...No elongation, wrinkles, or shrinkage.

×... Elongation and shrinkage [Effects of the invention] As mentioned above, it is formed by blending a curable phosphazene compound with a magnetic material as a binder on a support mainly made of a styrene polymer having a syndiotactic structure. By providing a magnetic layer that has a strong adhesive strength with the support, it has a high tensile modulus, and has excellent heat resistance, abrasion resistance, and solvent resistance, and also has excellent dispersibility of magnetic components. An excellent magnetic recording medium can also be obtained.

Therefore, the magnetic recording medium of the present invention has a long life and is also excellent in performance such as running stability and S/'N ratio.

Therefore, the magnetic recording medium of the present invention can be widely and effectively used in various fields of electronic materials and magnetic recording materials.

Claims (3)

[Claims] (1) A magnetic recording medium characterized by having a magnetic layer containing a curable phosphazene compound as a binder on a support mainly made of a styrene polymer having a syndiotactic structure. (2) A phosphazene compound has a general formula ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (In the formula, p and q are p>0, q>0, and p+q=
represents a real number satisfying 2, X represents a polymerizable curable group, and Y represents a polymerizable curable group or a non-polymerizable curable group. X and Y may be the same or different. 2. The magnetic recording medium according to claim 1, which has a repeating unit represented by ) and has a degree of polymerization of 3 or more. (3) A phosphazene compound is a compound in which repeating units represented by the general formula ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (in the formula, p, q, X and Y are the same as above) are bonded in a cyclic manner. The magnetic recording medium according to claim 1.